LU-4049 build: fix 'NULL pointer dereference' errors

LU-4049 build: fix 'NULL pointer dereference' errors

Fix 'NULL pointer dereference' defects found by Coverity version
6.6.1:
Dereference after null check (FORWARD_NULL)
For instance, Passing null pointer to a function which dereferences
it.
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.
Dereference null return value (NULL_RETURNS)

Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Change-Id: I1db4e80fd2c048cc20459e8da4cb61a97b3171cb
Reviewed-on: http://review.whamcloud.com/7827
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>