Add tests for tcms.bugs.views.New -- Refs #1598

[mfonism]

This PR adds (non-permissions related) tests for the view New in tcms/bugs/views.py as per #1598

• Permissions related tests already exists in tcms/bugs/tests/test_permissions.py

[mfonism]

@atodorov I'm having challenges writing tests for this part of the code:

https://github.com/kiwitcms/Kiwi/blob/master/tcms/bugs/views.py#L112-L114

The thing is, data['_execution'] is a string, and not a django model object, so data['_execution'].case.component.all() doesn't work.

I'm thinking data['_execution'] should be an integer representing the pk of a test_execution which can then be gotten using TestExecution.objects.get()