LU-1399 config: check lustre_cfg_new() return

LU-1399 config: check lustre_cfg_new() return

Check if lustre_cfg_new() fails its allocation and pass that error
on to the caller instead of dereferencing the NULL pointer.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I8a934777ea68a866f5f087a6c0948a6dbc3ebbe5
Reviewed-on: http://review.whamcloud.com/10739
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>