Improve error reporting in ConnDiags tests

If an exception is thrown before the callback is registered,
the finally{} block will fail with an exception explaining
the callback can't be unregistered. This masks the actual
exception.

This will ensure the original exception is printed instead.

Test: ConnectivityDiagnosticsManagerTest
Change-Id: I38aba86ff6d5d2a2a8a27c389feffd3aab788774
1 file changed