target/rd: Add checks for backend DIF emulation
target/rd: Add checks for backend DIF emulation

Make sure that RAMDISK only attempts to use backend DIF emulation
when it's actually enabled at device level.

Cc: Martin Petersen <0384aaef27f06874adbdb09a807bb339f4aff9fd@oracle.com>
Cc: Sagi Grimberg <380ce2a82d3d08e67ab163b51dc6d30288ad3f13@mellanox.com>
Signed-off-by: Nicholas Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs