RFR: 8087189: RMI server-side multiplex protocol support should be removed

[Roger Riggs]

Please review the removal of the RMI server-side multiplex protocol.
It is not in use and was disabled in JDK 9.

Webrev:
   http://cr.openjdk.java.net/~rriggs/webrev-rmi-multiplexer-8087189/

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8087189

Thanks, Roger