LU-11712 osd-ldiskfs: Wrap blk integrity with config check

LU-11712 osd-ldiskfs: Wrap blk integrity with config check

Build is currently broken for kernels without
CONFIG_BLK_DEV_INTEGRITY. Build failure introduced by LU-11096
commit c8505c2e70d03ba20edf9fcbf431888e87a21147
https://review.whamcloud.com/#/c/32725/
Use of blk integrity should be wrapped in the config check for
HAVE_BLK_INTEGRITY_ENABLED

Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: Iac9e4a2572024c026132c87c11042cf353b14d48
Reviewed-on: https://review.whamcloud.com/33745
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>