LU-3107 build: fix 'code maintainability' errors

LU-3107 build: fix 'code maintainability' errors

Fix 'code maintainability' issues found by Coverity version 6.5.1:
Unused pointer value (UNUSED_VALUE)
Pointer returned by function is never used.
Missing varargs init or cleanup (VARARGS)
va_end was not called for variable.

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: I5dd51c4332e966a5e4b274ff5c699a571931161c
Reviewed-on: http://review.whamcloud.com/5944
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: John Hammond <johnlockwoodhammond@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>