LU-8602 gss: Support GSS on linux 4.6+ kernels

LU-8602 gss: Support GSS on linux 4.6+ kernels

Currently the GSS code for Lustre directly uses the linux crypto API.
The GSS code uses struct crypto_hash which has now been removed in
newer kernels for struct crypto_ahash. It is possible in the future
that we could run into this issue again so to make porting easier
lets move the GSS code to the libcfs crypto api. That way in the
future when the linux crypto api changes the libcfs layer will handle
these changes so GSS will not need further patches. This patch also
exposes some of the libcfs crypto functions to user land as well.

Change-Id: I7baed64d0340ad864732a782ea401e2e0e9ae1b7
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/23289
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>