Do not force expected-xml

Do not force expected-xml

After using this for a few months now I'm convinced this is not the
right way to achieve what we want here. XML differences should be
informational and not build breaking. Pretty much every change
requires XML changes so I think this has been more annoying than
helpful.

This new patch removes expected-xml and instead outputs XML diffs
instead which can be stored in logs and reviewed.

Change-Id: Ia4039489502499df1b15a4d9fe1e553af3c5bfcd
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>