Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56600
Fix missing "return;" statements after sendError():
do not waste time generating response for PROPFIND requests that contain broken XML document.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1600955 13f79535-47bb-0310-9956-ffa450edef68