Remove priority from attribute constructor/destructor

On some platforms, the __attribute__ constructor and destructor won't
take priorities and the compilation failed.  On such platform would be
macOS.  For this reason, the constructor/destructor in the libisc was
reworked to not use priorities, but have a single constructor and
destructor that calls the appropriate routines in correct order.

This commit removes the extra priority because it's now not needed and
it also breaks a compilation on macOS with GCC 10.

(cherry picked from commit d68b009c)
80 jobs for !5104 with 2708-named-doesn-t-compile-with-gcc-10-v9_16 in 20 minutes and 48 seconds (queued for 9 seconds)
latest detached
Status Job ID Name Coverage
  Precheck
passed #1753483
amd64 linux
autoreconf

00:00:25

passed #1753485
amd64 linux
clang-format

00:00:26

passed #1753486
amd64 linux
coccinelle

00:03:31

passed #1753487
amd64 linux
danger

00:00:25

passed #1753484
amd64 linux
misc

00:00:24

passed #1753488
amd64 linux
tarball-create

00:00:25

 
  Build
passed #1753502
amd64 linux
clang:asan

00:04:00

passed #1753506
amd64 linux
clang:buster:amd64

00:02:02

passed #1753509
amd64 libvirt
clang:freebsd12:amd64

00:01:54

passed #1753510
amd64 libvirt
clang:freebsd13:amd64

00:03:45

passed #1753511
amd64 libvirt
clang:openbsd:amd64

00:03:21

passed #1753504
amd64 linux
clang:tsan

00:02:14

passed #1753489
amd64 linux
gcc:alpine3.13:amd64

00:01:48

passed #1753501
amd64 linux
gcc:asan

00:03:32

passed #1753499
amd64 linux
gcc:bionic:amd64

00:02:09

passed #1753493
amd64 linux
gcc:buster:amd64

00:01:57

passed #1753490
amd64 linux
gcc:centos7:amd64

00:01:37

passed #1753491
amd64 linux
gcc:centos8:amd64

00:01:40

passed #1753500
amd64 linux
gcc:focal:amd64

00:01:54

passed #1753505
amd64 linux
gcc:mutexatomics

00:01:48

passed #1753495
amd64 linux
gcc:out-of-tree

00:01:46

passed #1753494
amd64 linux
gcc:sid:amd64

00:02:32

passed #1753497
i386 linux
gcc:sid:i386

00:01:45

passed #1753507
amd64 linux
gcc:softhsm2.4

00:01:49

passed #1753508
amd64 linux
gcc:softhsm2.6

00:01:56

passed #1753492
amd64 linux
gcc:stretch:amd64

00:02:04

passed #1753496
amd64 linux
gcc:tarball

00:02:16

passed #1753503
amd64 linux
gcc:tsan

00:02:20

passed #1753498
amd64 linux
gcc:tumbleweed:amd64

00:01:41

passed #1753513
amd64 windows
msvc:windows:amd64

00:01:07

passed #1753512
amd64 linux
nolibtool:sid:amd64

00:02:23

 
  Unit
passed #1753525
amd64 linux
unit:clang:asan

00:01:17

passed #1753529
amd64 linux
unit:clang:buster:amd64

00:00:38

passed #1753532
amd64 libvirt
unit:clang:freebsd12:amd64

00:01:04

passed #1753533
amd64 libvirt
unit:clang:freebsd13:amd64

00:02:58

passed #1753527
amd64 linux
unit:clang:tsan

00:01:31

passed #1753514
amd64 linux
unit:gcc:alpine3.13:amd64

00:01:06

passed #1753524
amd64 linux
unit:gcc:asan

00:01:10

passed #1753522
amd64 linux
unit:gcc:bionic:amd64

00:00:41

passed #1753518
amd64 linux
unit:gcc:buster:amd64

00:01:00

passed #1753515
amd64 linux
unit:gcc:centos7:amd64

00:00:39

passed #1753516
amd64 linux
unit:gcc:centos8:amd64

00:00:39

passed #1753523
amd64 linux
unit:gcc:focal:amd64

00:00:39

passed #1753528
amd64 linux
unit:gcc:mutexatomics

00:00:36

passed #1753519
amd64 linux
unit:gcc:sid:amd64

00:00:36

passed #1753520
i386 linux
unit:gcc:sid:i386

00:00:43

passed #1753530
amd64 linux
unit:gcc:softhsm2.4

00:00:39

passed #1753531
amd64 linux
unit:gcc:softhsm2.6

00:00:50

passed #1753517
amd64 linux
unit:gcc:stretch:amd64

00:00:44

passed #1753526
amd64 linux
unit:gcc:tsan

00:01:48

passed #1753521
amd64 linux
unit:gcc:tumbleweed:amd64

00:00:37

passed #1753534
amd64 linux
unit:nolibtool:sid:amd64

00:00:49

 
  System
passed #1753546
amd64 linux
system:clang:asan

00:13:11

passed #1753550
amd64 linux
system:clang:buster:amd64

00:11:08

passed #1753553
amd64 libvirt
system:clang:freebsd12:amd64

00:10:53

passed #1753554
amd64 libvirt
system:clang:freebsd13:amd64

00:12:42

passed #1753548
amd64 linux
system:clang:tsan

00:14:40

passed #1753535
amd64 linux
system:gcc:alpine3.13:amd64

00:12:03

passed #1753545
amd64 linux
system:gcc:asan

00:13:35

passed #1753543
amd64 linux
system:gcc:bionic:amd64

00:10:45

passed #1753539
amd64 linux
system:gcc:buster:amd64

00:12:52

passed #1753536
amd64 linux
system:gcc:centos7:amd64

00:11:17

passed #1753537
amd64 linux
system:gcc:centos8:amd64

00:12:01

passed #1753544
amd64 linux
system:gcc:focal:amd64

00:11:07

passed #1753549
amd64 linux
system:gcc:mutexatomics

00:11:26

passed #1753540
amd64 linux
system:gcc:sid:amd64

00:10:45

passed #1753541
i386 linux
system:gcc:sid:i386

00:09:36

passed #1753551
amd64 linux
system:gcc:softhsm2.4

00:11:33

passed #1753552
amd64 linux
system:gcc:softhsm2.6

00:12:13

passed #1753538
amd64 linux
system:gcc:stretch:amd64

00:10:44

passed #1753547
amd64 linux
system:gcc:tsan

00:15:24

passed #1753542
amd64 linux
system:gcc:tumbleweed:amd64

00:11:54

passed #1753555
amd64 linux
system:nolibtool:sid:amd64

00:11:16

 
  Docs
passed #1756870
amd64 linux
docs

00:02:16

failed #1753556
amd64 linux
docs

00:02:37

 
  Postcheck
passed #1753560
amd64 linux
cppcheck

00:00:41

passed #1753557
amd64 linux
flake8

00:00:39

passed #1753561
amd64 linux
gcov

00:00:35

76.0%
passed #1753558
amd64 linux
pylint

00:00:45

passed #1753559
amd64 linux
scan-build

00:09:50