make client integration tests hit local docker web server

[pedritom-amzn]

problem: the python client integration tests currently hit the prod api since the endpoint is hardcoded into the client.

impact: lack of isolation. the success of the tests depend on whether prod is up and working. also, the tests unnecessarily add test load and risk to prod.

proposal: make client integration tests hit the local docker web server instead of the prod api so as to provide some isolation and make things more self-contained.