Use xml.dom.minidom and xmlutils in unit tests

This is an example using xml parsing in existing unit
tests instead of assertIn and string comparisons to verify
workflow generation.  It's much less fragile.

If folks like this, we can change other tests similarly.

Change-Id: Ib1c266933a4a3104af34586527148c2612019000
Merge "Use xml.dom.minidom and xmlutils in unit tests"