xfs_dqrele_inode calls xfs_iput to release the ilock and a reference
and then also calls IRELE which does a second decrement of the reference
count.  This leads to a premature freeing of inodes when quotas were turned
off while the filesystem was mounted.

Thanks to Utako Kusaka for reporting the bug and provinding a good testcase.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Utako Kusaka <u-kusaka@wm.jp.nec.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>