Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=51905

Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=51905
Skip attempt to shutdown AprEndpoint acceptor threads if the server socket has been already forcefully closed.
Reduce waiting timeout from 30s to 10s. I think if things go wrong 10s is enough to wait.

If it were waiting 30s
- the JVM itself might be forcefully closed by service wrapper as unresponsive.
- it must print something to the logs, otherwise it looks odd.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1176799 13f79535-47bb-0310-9956-ffa450edef68