Modify PMT upgrade tests for directory environments

The beaker host['distmoduledir'] variable is not meaningful if the
host is using directory environments (e.g 'production').

This commit updates the PMT upgrade tests to use the default
module directory if the test does not explicitly call for one.
Merge branch 'pmt_directory_env_support' into uber_pmt
Patch 3.7 install -- cherry pick after env_support is merged