staging/lustre: 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>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3107
Lustre-change: http://review.whamcloud.com/5944


Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John Hammond <johnlockwoodhammond@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>