tests: Add new tests for backup-rename command

tests: Add new tests for backup-rename command

Extend the existing 'backup online' tests to also test the domain
rename case. This mostly involves some extra assertions that the
restored DB has been modified appropriatelt (i.e. domain NetBIOS
name is updated, etc).

I've also added an extra test case that creates a few objects and
links and specifically asserts that they get renamed appropriately.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>