LU-6261 gnilnd: Use kgnilnd_vzalloc to allocate fma blocks.

LU-6261 gnilnd: Use kgnilnd_vzalloc to allocate fma blocks.

In low memory situations we may not be able to allocate memory.
vmalloc tries forever to get memory.
Use kgnilnd_vzalloc which uses the GFP_NOFS flag for allocating
memory for fma blocks.

Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I18f8564424abfc9c63e675ac98ca61487b5a2b34
Reviewed-on: http://review.whamcloud.com/15438
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>