Remove nailgun entity_mixin import from discovery tests

[Gauravtalreja1]

Problem Statement

Remove nailgun entity_mixin import from discovery tests, and replace entity_mixins.DEFAULT_SERVER_CONFIG

Solution

Replacing entity_mixins.DEFAULT_SERVER_CONFIG with new default_nailgun_config method, which is same as existing user_nailgun_config method
And, we don't have any automated tests under this module, verifying default_nailgun_config() method in #15163

[synkd]

Can you please explain the rationale for adding a new function for this instead of passing the admin credentials to user_nailgun_config?

[Gauravtalreja1]

yes, its indeed possible, but I just wanted to keep it separate from existing user_nailgun_config, as similar to what we had in nailgun. entity_mixin and its using get_credentials func to get creds so we don't need to pass and import settings just for ssh username and passwd in the tests

[synkd]

I'm not totally convinced that adding a function with very similar functionality to an existing function is preferable to importing settings in a test module, especially since #9936 suggests that user_nailgun_config can be used with both admin and non-admin users. I won't block the PR based on that, though.

However, I do think the name of the function and the docstring should make it clear why the new function exists. I would suggest changing the name of the function to admin_server_config, since it is designed specifically to return a ServerConfig object with the admin credentials. In the docstring, I would remove the reference to :param user: since the function has no parameters, and I would also make it clear in the docstring that the config file will be constructed from the admin credentials.

What do you think about these suggestions?

[Gauravtalreja1]

@synkd Good point, renamed the func and updated the docstrings