xfs: Remove some useless flags tests

'flags' have XFS_ALL_QUOTA_ACCT cleared immediately on function entry.
There's no point in checking these bits later in the function. Also
because we check something is going to change, we know some enforcement
bits are being added and thus there's no point in testing that later.

Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>