Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55937
Treat a context path of "/ROOT" as equivalent to "" (i.e. it is treated as the ROOT application).
Note that when deploying an application via the manager text interface to /ROOT, it was deployed as the ROOT application but reported that the deployment had failed. It now deploys it as the ROOT application and reports a successful deployment to the context path "/"

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1556788 13f79535-47bb-0310-9956-ffa450edef68