Revert "nfsd4: support change_attr_type attribute"

This reverts commit a8585763.

We're still factoring ctime into our change attribute even in the
IS_I_VERSION case.  If someone sets the system time backwards, a client
could see the change attribute go backwards.  Maybe we can just say
"well, don't do that", but there's some question whether that's good
enough, or whether we need a better guarantee.

Also, the client still isn't actually using the attribute.

While we're still figuring this out, let's just stop returning this
attribute.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>