block: Fix regression in sed-opal for a saved key.

The commit 3bfeb612
introduced the use of keyring for sed-opal.

Unfortunately, there is also a possibility to save
the Opal key used in opal_lock_unlock().

This patch switches the order of operation, so the cached
key is used instead of failure for opal_get_key.

The problem was found by the cryptsetup Opal test recently
added to the cryptsetup tree.

Fixes: 3bfeb612 ("block: sed-opal: keyring support for SED keys")
Tested-by: Ondrej Kozina <okozina@redhat.com>
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Link: https://lore.kernel.org/r/20231003100209.380037-1-gmazyland@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>