ocfs2: fix unbalanced locking

Based on what fails, function can return with nfs_sync_rwlock either
locked or unlocked. That can not be right.

Always return with lock unlocked on error.

Fixes: 4cd9973f

 ("ocfs2: avoid inode removal while nfsd is accessing it")
Signed-off-by: Pavel Machek (CIP) <pavel@denx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Link: http://lkml.kernel.org/r/20200724124443.GA28164@duo.ucw.cz


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>