RFR 9: 8066750 Remove HTTP proxy implementation and tests from RMI

[Roger Riggs]

The RMI http proxy mechanism was deprecated in Java SE 8.
Please review the removal of now dead code for the RMI Http proxy 
implementation and tests.

Webrev:
   http://cr.openjdk.java.net/~rriggs/webrev-httpproxy-8066750/

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8066750

Thanks, Roger