xfs: cover the log on freeze instead of cleaning it

Filesystem freeze cleans the log and immediately redirties it so log
recovery runs if a crash occurs after the filesystem is frozen. Now
that log quiesce covers the log, there is no need to clean the log and
redirty it to trigger log recovery because covering has the same
effect. Update xfs_fs_freeze() to quiesce (and thus cover) the log.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>