rename docker-compose.test.yml to something else

[lenazun]

re: https://redmine.eff.org/issues/17010

Ben says:
We'd like to fix automated phantomdc docker image builds on docker hub. These are supposed to get triggered by changes to the "master" branch on the phantomdc github repo. We can't currently do this because there is a file called docker-compose.test.yml in the git repo. This is a reserved name on docker hub, repos that contain files with that name must conform to certain standards. The easiest fix may be to just rename this file to something that doesn't end in test.yml for example docker-compose.testing.yml. Alternatively you could try adding the sut service described in the linked docs. Be warned, the docs are for docker cloud which is closely related-to but not the same as docker hub. I don't believe there are current docs for docker hub automated testing.