xfs: allow individual quota grace period extension

xfs: allow individual quota grace period extension

The only grace period which can be set in the kernel today is for id 0,
i.e. the default grace period for all users.  However, setting an
individual grace period is useful; for example:

 Alice has a soft quota of 100 inodes, and a hard quota of 200 inodes
 Alice uses 150 inodes, and enters a short grace period
 Alice really needs to use those 150 inodes past the grace period
 The administrator extends Alice's grace period until next Monday

vfs quota users such as ext4 can do this today, with setquota -T

To enable this for XFS, we simply move the timelimit assignment out
from under the (id == 0) test.  Default setting remains under (id == 0).
Note that this now is consistent with how we set warnings.

(Userspace requires updates to enable this as well; xfs_quota needs to
parse new options, and setquota needs to set appropriate field flags.)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>