ext4: fix possible leak of s_journal_flag_rwsem in error path

Fixes: c8585c6f ("ext4: fix races between changing inode journal ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 4.7