Added more unit tests for embargo

Tests for embargo are working now and this includes more coverage. The following scenarios are tested:

Work goes in embargo
 - Owner can see it in search results and show view
 - Member of group with access can see it in search results and show view
 - Non-logged-in user cannot see it in search results or show view

Work goes out of embargo
  - Owner can still see it in search results and show view
  - Member of group with access can still see it in search results and show view
  -  Non-logged-in user can now see it in search results and show view