Added testcase in ganetiviz/tests that verifies format of cluster json data returned

refs #14967
Added view for selenium unit tests in  ganetiviz/tests/views.py

refs #14967
Improved the ganetiviz tests
  - Removed outmoded test mixins & redundant lines
  - Renamed views.py to test_views.py

refs #14967
Corrected a small error in  selenium unittest in ganetiviz/tests

refs #14967
Improved ganetiviz tests code - pep8-ified tests

refs #14967
Added appropriate delete calls to tearDown method in ganetiviz tests

refs #14967
Fixed a small bug in the ganetiviz tests
    - Code was creating a duplicated Node object

refs #14967
Shifted ganetiviz tests to ganeti_webmgr/ganeti_webmgr/ganetiviz/tests as per new gwm layout