Code Review 7008595: Class loader leak caused by keepAliveTimer thread in KeepAliveCache

[Chris Hegarty]

Alan, Michael,

Trivially, set the thread context classloader to null for the keep-alive 
timer and cache cleaner threads.

http://cr.openjdk.java.net/~chegar/7008595/webrev.00/webrev/

Thanks,
-Chris.