ServiceDiscoveryManager test coverage

[Patricia Shanahan]

As indicated in the "TaskManager Progress" thread, I think, based on 
reading the source code, that there is a concurrency bug in 
ServiceDiscoveryManager.LookupCacheImpl's addProxyReg method.

I added logging to see which tests I should run to evaluate a fix. As 
far as I can tell, the automated system contains a single test that 
creates a ServiceDiscoveryManager, LeaseRenewDurRFE, and it does not 
appear to use addProxyReg.

Are there any tests in addition to the QA and JTreg tests that might 
cover this?

Patricia