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.
Merge pull request #1804 from kbidarkar/fix-ui-tests1

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