Closing ApplicationRegistry components can NPE and prevent others cleanly shutting down

The ApplicationRegistry has a close() method that peforms close() on a number of broker components.

However, it currently has a rather ugly structure:
try : close finally : try : close : finally ....

Also the items that are being closed need to be null tested in case there was an error during broker startup.

Refactor all the close methods so that they do not throw Exceptions as there is nothing we can do but report it during shutdown.

This is particularly annoying as QpidTestCase runs will fail and hide the true cause of the failure.