Fix NPEs in test

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1553605 13f79535-47bb-0310-9956-ffa450edef68
Clarify based on feedback on users@ list

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1553608 13f79535-47bb-0310-9956-ffa450edef68
Be more precise about how maxConnections works

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1553650 13f79535-47bb-0310-9956-ffa450edef68