Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56223
Throw an IllegalStateException if a call is made to ServletContext.setInitParameter() after the ServletContext has been initialized

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1574944 13f79535-47bb-0310-9956-ffa450edef68