Fix for NPE introduced by r1559707 that caused ELParser test to fail.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1559798 13f79535-47bb-0310-9956-ffa450edef68
Refactor cookie name validation into a helper class to prepare for enabling RFC6265.
This should have no functional change.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1559801 13f79535-47bb-0310-9956-ffa450edef68