Fixed some UI tests related to hw_model, p_table and hostgroups.

* Updated data as per tests.
* Drop length arguments to `gen_*` methods. They produce 10 chars
  long strings by default
* Removed skips related to old bugs.
* Many other miscellaneous fixes.
If success notification is not working for any entity/test then I think blocking the test with bz_id would be best in my opinion.