Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=57091
Work around the behaviour of the Oracle JRE when creating new threads in an applet environment that breaks the WebSocket client implementation.
Patch provided by Niklas Hallqvist.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1633688 13f79535-47bb-0310-9956-ffa450edef68