Enable XML testing for test_server_addresses

This commit enables XML testing for the tests in
test_server_addresses.py. Previously the tests were only run with
JSON. This commit adds a new class to run the tests with the XML
client.

Change-Id: I495cb3cefc45a59f282c207d50b53f8b86b3d10e
Merge "Enable XML testing for test_server_addresses"