Refactored negative server metadata tests into seperate module

* Merged server negative metadata tests from other modules
  into one
* Added assertRaises to test_set_blank_metadata_dict as an
  exception is the expected behavior

Change-Id: I1e9fcfc7c8d3da9a5f2425e8403a92aca6a75188
Merge "Refactored negative server metadata tests into seperate module"