xfs: untangle SYNC_WAIT and SYNC_TRYLOCK meanings for xfs_qm_dqflush

Only skip pinned dquots if SYNC_TRYLOCK is specified, and adjust the callers
to keep the behaviour unchanged.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_dquot_item.c b/fs/xfs/xfs_dquot_item.c
index 79da711..3956e1b 100644
--- a/fs/xfs/xfs_dquot_item.c
+++ b/fs/xfs/xfs_dquot_item.c
@@ -133,7 +133,7 @@
 	 * lock without sleeping, then there must not have been
 	 * anyone in the process of flushing the dquot.
 	 */
-	error = xfs_qm_dqflush(dqp, 0);
+	error = xfs_qm_dqflush(dqp, SYNC_TRYLOCK);
 	if (error)
 		xfs_warn(dqp->q_mount, "%s: push error %d on dqp %p",
 			__func__, error, dqp);