Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=56840
BZ56840: Tomcat gets the context path from the URI (rather than from the mapping data, which is another possible source) so it is not possible to reset it before getting it.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1617471 13f79535-47bb-0310-9956-ffa450edef68