LU-5349 include: use __vmalloc() to avoid __GFP_FS default

LU-5349 include: use __vmalloc() to avoid __GFP_FS default

When possible, try to Direct use of __vmalloc() which allows
for protection flag specification, and particularly to not
set __GFP_FS, which can cause some deadlock situations in our
code.

This patch is the b2_5 back-port of :
Lustre-commit: 635421641bfa8a412edebd4ffbbdf05fd0c47410
Lustre-change: http://review.whamcloud.com/11190/

Also corrects a typo in __OBD_VMALLOC_VERBOSE name.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: I588ebf27d1ff7538745b732d174696c379107ea3
Reviewed-on: http://review.whamcloud.com/11739
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>