Update robottelo's list of API paths

Several new API paths have been added.

* @cfouant can vouch for the `activation_keys` paths.
* jsherrill can vouch for the new `errata` path.
* mmccune can vouch for the new `mail_notifications` paths.
* partha can vouch for the `docker_images` and `docker_tags` paths.

There is a bug in apipie, so these paths differ from what the server currently
returns. This bug is described in BZ 1166875. Make the test code accomodate this
bug.