xfs: poll waiting for quotacheck

Create a pwork destroy function that uses polling instead of
uninterruptible sleep to wait for work items to finish so that we can
touch the softlockup watchdog.  IOWs, gross hack.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/xfs_qm.c

@@ -1300,7 +1300,7 @@ xfs_qm_quotacheck(
 		flags |= XFS_PQUOTA_CHKD;
 	}
 
-	error = xfs_iwalk_threaded(mp, 0, xfs_qm_dqusage_adjust, 0, NULL);
+	error = xfs_iwalk_threaded(mp, 0, xfs_qm_dqusage_adjust, 0, true, NULL);
 	if (error)
 		goto error_return;