CtsTestServer: Don't always use one port

Don't always use port 4444 / 4445 for running the CTS
test server. This has the following advantages:

1) Tests can now be run in parallel.
2) Tests have different port numbers, helping eliminate interaction
between different tests.

Bug: 6392702
Change-Id: Ic7b2fa38117e0ffac8006e3516821bacaf01ace5
1 file changed