LU-2800 autoconf: block device release changed in newer kernels.

LU-2800 autoconf: block device release changed in newer kernels.

For kernels at 3.10 and above the release method for block
devices no longer return a integer. This impacts the lloop
block device we use on the lustre client side.

Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: Ib63e2897a48989f1cf5185a1c88a5ddbf989c0a9
Reviewed-on: http://review.whamcloud.com/5380
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>