Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55978
Ensure that container makes first call on onWritePossible when using non-blocking IO with an HTTP upgraded connection

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1557092 13f79535-47bb-0310-9956-ffa450edef68