Fix injecting of EventBus into DiscoveryClient

Discovery client currently does a bunch of stuff in the constructor.
These operations previous saw a null eventBus because it is optional.
The fix ensures that the optional EventBus is properly resolved before
the constructor is called
Disable the DiscoveryStatusCheckTest until we can write a more robust
mock server.
Minor cleanup
Merge pull request #126 from elandau/master

Fix injecting of EventBus into DiscoveryClient