Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=55633 for APR.
If the socket was registered for read and write and only one occurred, the registration for the other event was lost. Ensure that the socket is re-registered with the Poller when necessary.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1530081 13f79535-47bb-0310-9956-ffa450edef68