RFR 8185719 [testlibrary] : RMI TestSocketFactory does not flush

[Roger Riggs]

Please review a correction in the RMI TestSocketFactory 
MatchReplaceOutputStream to correctly flush
partial matches.  It can cause hangs when the one or more bytes before a 
flush are a partial match
for the pattern and the consumer is waiting for the pending bytes.

Webrev:
   http://cr.openjdk.java.net/~rriggs/webrev-flush-8185719/index.html

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8185719

Thanks, Roger