LU-1961 build: fix 'dereference before null check' errors

LU-1961 build: fix 'dereference before null check' errors

Fix 'dereference before null check' defects found by Coverity version
6.0.3:
Dereference before null check (REVERSE_INULL)
Null-checking variable suggests that it may be null, but it has
already been dereferenced on all paths leading to the check.

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: I0c1be27ea443865fcb7640976839d95d0dc07b9a
Reviewed-on: http://review.whamcloud.com/4023
Tested-by: Hudson
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>