[Epic] Enable bindings-based tests
We currently don't test the bindings, which means we aren't ensuring the openAPI schema Pulp generates is correct, and that the bindings it creates are usable. For example sometimes APIs are added, which don't have their bindings available or working.
Also we want to make tests quicker/easier to write. Switching to bindings allows the test writer to work at a higher level and cover more functionality more quickly. Instead of interacting with Pulp using an HTTP library like requests, you'll work in terms of Pulp's operations themselves. For example, look at the large amount of functionality in this not-long script: https://github.com/pulp/pulpcore/blob/master/.travis/test_bindings.py
This isn't designed to replace all raw-http interaction.