Persisting solr.xml still adds some elements that aren't in the original

From elyograg: distribUpdateSoTimeout="0" distribUpdateConnTimeout="0" are added to the <cores> element when persisted.

The problem with the current test is it have everything I could think of in it, and they are all preserved. Adding a test that has only the minimal solr.xml should flush out persisting the attribs not in the original.