Don't process remaining dispatch requests once the socket has been closed.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1518845 13f79535-47bb-0310-9956-ffa450edef68
Refactor SocketWrapper
 - make fields private
 - add reset() method to wrapper
 - distribute resetting of values between SocketWrapper and KeyAttachment so each resets its own fields

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1518846 13f79535-47bb-0310-9956-ffa450edef68