ext4 crypto: exit cleanly if ext4_derive_key_aes() fails
ext4 crypto: exit cleanly if ext4_derive_key_aes() fails

Return value of ext4_derive_key_aes() is stored but not used.
Add test to exit cleanly if ext4_derive_key_aes() fail.
Also fix coverity CID 1309760.

Signed-off-by: Laurent Navet <049659cdfcbbaec8e29d19668ed7e4a1a04d7a9f@gmail.com>
Signed-off-by: Theodore Ts'o <4ed386e0495d3e109932df055831d9ec2f824927@mit.edu>

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