Added two tests for activation key copy

First test verifies that you cannot use a name already taken.
Second test verifies that subscriptions are being copied over.
```
@Test: Copy activation key with duplicate name ... ok
@Test: Copy Activation and verify contents ... ok
```
Bonus: Added the beginings of an activation key search.
So, which of these is more useful?

* An unchanging error message produced by Robottelo.
* An error code generated by hammer.