quota: Remove BUG_ON from dqget()

[ Upstream commit 249f374eb9b6b969c64212dd860cc1439674c4a8 ]

dqget() checks whether dquot->dq_sb is set when returning it using
BUG_ON. Firstly this doesn't work as an invalidation check for quite
some time (we release dquot with dq_sb set these days), secondly using
BUG_ON is quite harsh. Use WARN_ON_ONCE and check whether dquot is still
hashed instead.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit c08d02053b9e98dffea9b9b378dc90547e4621e8)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>