[#66147100] remove the cli option for mocking

Remove the cli option to enable fog mocking. None of other tools have one and
people use an environment variable to use it anyway.

Also move the enabling of fog mocking via an environment variable to the spec_helper
instead of in the class.
Merge pull request #42 from gds-operations/66147100_remove_cli_option_for_fog_mock_mode

[#66147100] remove the cli option for mocking