Remove all non-GA plugins from the single container

[bmbouter]

The single container ships plugins that are not GA'd currently. Specifically, the ones below. The expectation from users that I have is that the single container could be run in production so having these non GA plugins there is not aligned with that. We can add them back when they are GA, or later we can make another container that is for more experimental plugins.

pulp-cookbook 0.1.0b9
pulp-gem 0.0.1b2
pulp-npm 0.1.0a4
pulp-ostree 2.0.0a6

This change would be to remove these from the single container.