better system test entropy

- use genrandom to get 4k of data instead of 800 bytes
- set this value as RANDOMSIZE in conf.sh

(cherry picked from commit 19aaecaf)
19 jobs for systest-entropy-v9_11 in 11 minutes and 28 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #98400
amd64 docker linux

00:00:16

 
  Build
passed build:centos:centos6:amd64 #98401
amd64 docker linux

00:02:17

passed build:centos:centos7:amd64 #98402
amd64 docker linux

00:02:33

passed build:debian:sid:amd64 #98403
amd64 docker linux

00:02:00

passed build:debian:sid:i386 #98404
i386 docker linux

00:01:48

passed noassert:build:debian:sid:amd64 #98405
amd64 docker linux

00:01:47

 
  Test
passed docs:debian:sid:amd64 #98406
amd64 docker linux

00:00:57

passed install:debian:sid:amd64 #98415
amd64 docker linux

00:02:05

passed noassert:systemtest:debian:sid:amd64 #98417
amd64 docker linux

00:04:35

passed noassert:unittest:debian:sid:amd64 #98416
amd64 docker linux

00:00:55

passed systemtest:centos:centos6:amd64 #98411
amd64 docker linux

00:04:12

passed systemtest:centos:centos7:amd64 #98412
amd64 docker linux

00:04:31

passed systemtest:debian:sid:amd64 #98421
linux docker amd64

00:04:00

passed systemtest:debian:sid:i386 #98414
i386 docker linux

00:04:23

passed unittest:centos:centos6:amd64 #98407
amd64 docker linux

00:01:08

passed unittest:centos:centos7:amd64 #98408
amd64 docker linux

00:01:03

passed unittest:debian:sid:amd64 #98409
amd64 docker linux

00:01:10

passed unittest:debian:sid:i386 #98410
i386 docker linux

00:01:09

failed systemtest:debian:sid:amd64 #98413
amd64 docker linux

00:04:26