Backport r1567429 from tomcat/trunk:
One more followup to r1567148
Assert that version of merged web.xml is dictated by webapp's web.xml file, not by default one.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1567433 13f79535-47bb-0310-9956-ffa450edef68