Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55642
Correct logic error in Node.isLiteral() that was returning the inverse of the desired result when the value was an EL expression.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1530632 13f79535-47bb-0310-9956-ffa450edef68