gfs2: Lock imbalance on error path in gfs2_recover_one

In gfs2_recover_one, fix a sd_log_flush_lock imbalance when a recovery
pass fails.

Fixes: c9ebc4b7 ("gfs2: allow journal replay to hold sd_log_flush_lock")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>