Add optional check for OBS published XML
Add optional check for OBS published XML

The OpenBuildService has a published XML format with packages and
versions. Add an optional parameter "--obs-published-xml" which
points to an xml file. If that parameter is given, also evaluate
the xml file and output the version from the OBS xml in the tables.

Change-Id: I74d56a538c17192f8132814eaa7f207bf14577e9

openstack/rpm-packaging-tools