Simplify

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1515433 13f79535-47bb-0310-9956-ffa450edef68
Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55438
Don't call onAllDataRead() twice for an empty request body.
Make the non-blocking test more robust as on client disconnect the error may occur in the read or the write listener.
Unit test provided by Daniel Mikusa.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1515454 13f79535-47bb-0310-9956-ffa450edef68