Test_plugin_* jobs being renamed

I'm renaming test_plugin_* jobs for Foreman plugins to contain the
branch name that they're testing, e.g. test_plugin_foreman_docker is now

This might cause a little disruption to plugin PRs for a couple of hours
while the rename is applied to the PR tester and Jenkins finishes
testing the new jobs. Hopefully it'll be an improvement anyway as the
new job definitions are more reliable and are likely to remain more
green than what's there now.

(The reason's simply that it's easier to add jobs in JJB for multiple
branches, like foreman_discovery has, when the name contains the branch

ยทยทยท -- Dominic Cleal Red Hat Engineering