LU-11770 misc: fix bdev_integrity_enabled definition

LU-11770 misc: fix bdev_integrity_enabled definition

part of the patch was missed when it was backported
to b2_12, as a result bdev_integrity_enabled will
always defined as a function just returns false.

Change-Id: I9c9a83f3011f939e7f6d72140c08943d82a5416d
Fixes: b14e6617b9 ("LU-11770 osc: allow build without blk_integrity or crc-t10pi")
Test-Parameters: trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/37167
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>