LU-4357 libcfs: restore __GFP_WAIT flag to memalloc calls

LU-4357 libcfs: restore __GFP_WAIT flag to memalloc calls

In 2.4, the flags passed to the memory allocation functions are
translated from CFS enumeration values types to the kernel GFP
values by calling cfs_alloc_flags_to_gfp(). This function adds
__GFP_WAIT to all flags except CFS_ALLOC_ATOMIC. In 2.5, when
the cfs wrappers were dropped, cfs_alloc_flags_to_gfp() was
removed and the CFS_ALLOC_xxxx was simply replaced with __GFP_xxxx.
This means that most memory allocation calls are missing the
__GFP_WAIT flag. The result is that Lustre experiences more ENOMEM
errors, many of which the higher levels of Lustre do not handle
robustly.
Notes GFP_NOFS = __GFP_WAIT | __GFP_IO. So the patch replaces
__GFP_IO with GFP_NOFS.
Patch does not add __GFP_WAIT to GFP_IOFS. GFP_IOFS was not used in
2.4 so it has never been used with __GFP_WAIT.

Lustre-commit: e6b3d5de62b43a8702aa2dbda4a0bc6b6b10b5c2
Lustre-change: http://review.whamcloud.com/9223

Signed-off-by: Ann Koehler <amk@cray.com>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: I8f0341c34e595d437c06a4564a11e4c52bd4363a
Reviewed-on: http://review.whamcloud.com/9382
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>