Reworked how cli reads mode

Moved the code to read the config to the point where we're
actually looking up the mode rather than doing it at
module level. This way we can stub out the readconfig
and actually have it take effect when creating new instances.
Force CLI mode on execute, not suite setup.

We had a bunch of tests that were using the suite to execute,
but not for mocking, so it didn't go through the suite/test setup
logic that forced the cli mode. Moved the mode change to the execute
method so it's always on.