modified end_all_calls to end all calls on all phones by default

See comment in end_all_calls...

                #Don't worry about ending calls for phones that were not responsive at setup.
                #because those phones won't have any active calls anyway.
                #Users should be able to "Setup" phones that don't actually exist,
                #doing so should not cause any test failures. "Setup Phone" and "End All Calls"
                #should never cause test failures, since they are meant to be used in test 
                #setups and teardowns, not in test cases.