Most of the code from dynamic_inventory.py was moved to lib/generate.py
in order to consolidate the inventory code into one place.
Code changes from dynamic_inventoy.py to generate.py:
argparse and sys imports removed
args function definition removed
__main__ section removed
The `args` function was left in dynamic_inventory.py in order to ensure
the environment argument can use the relative path for
playbooks/inventory/env.d. As such, dynamic_inventory.py is imported in
order to provide test coverage.
Imports and coverage reports for tests were also updated.
Change-Id: Icd1ea365befd8e805dc2c48332c104bcd887899b