address unchecked return values

(cherry picked from commit ccfd5777)
18 jobs for 702-unchecked-returns-in-server-c-v9_12 in 7 minutes and 59 seconds (queued for 17 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #101444
amd64 docker linux

00:00:18

 
  Build
passed build:centos:centos6:amd64 #101445
amd64 docker linux

00:02:28

passed build:centos:centos7:amd64 #101446
amd64 docker linux

00:02:42

passed build:debian:sid:amd64 #101447
amd64 docker linux

00:01:56

passed build:debian:sid:i386 #101448
i386 docker linux

00:01:59

passed noassert:build:debian:sid:amd64 #101449
amd64 docker linux

00:02:11

 
  Test
passed docs:debian:sid:amd64 #101450
amd64 docker linux

00:00:50

passed install:debian:sid:amd64 #101459
amd64 docker linux

00:01:32

passed noassert:systemtest:debian:sid:amd64 #101461
amd64 docker linux

00:04:54

passed noassert:unittest:debian:sid:amd64 #101460
amd64 docker linux

00:00:48

passed systemtest:centos:centos6:amd64 #101455
amd64 docker linux

00:04:50

passed systemtest:centos:centos7:amd64 #101456
amd64 docker linux

00:04:57

passed systemtest:debian:sid:amd64 #101457
amd64 docker linux

00:04:54

passed systemtest:debian:sid:i386 #101458
i386 docker linux

00:04:48

passed unittest:centos:centos6:amd64 #101451
amd64 docker linux

00:00:53

passed unittest:centos:centos7:amd64 #101452
amd64 docker linux

00:00:52

passed unittest:debian:sid:amd64 #101453
amd64 docker linux

00:00:49

passed unittest:debian:sid:i386 #101454
i386 docker linux

00:00:47