(PUP-3248) Fix PMT tests for directory environment

The beaker host['distmoduledir'] variable is not meaningful if the
host is using directory environments (e.g. 'production').

This commit updates the helper methods for validating that a module
is (or is not) installed on the host by iterating over the
modulepath if a specific modulepath is not provided.

The calls to these helper methods have been updated for the change
in parameter ordering in the helper methods.
@jpartlow this is really a beaker bug which I have filed as QENG-1263.

The DEFAULT_GIT_ENV is what beaker uses internally to create the path for the puppet command and appears to ensure that the puppet command can be found on Windows.