Delete module user when module run finished

[abalakh]

Closes SatelliteQE/airgun#3

pytest tests/foreman/ui_airgun  (dev|…)
============================= test session starts ==============================
platform darwin -- Python 3.6.4, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
shared_function enabled - OFF - scope:  - storage: file
rootdir: /Users/andrii/workspace/robottelo, inifile:
plugins: wait-for-1.0.9, xdist-1.22.0, services-1.2.1, mock-1.6.3, forked-0.2
collected 7 items
2018-03-05 18:40:22 - conftest - DEBUG - BZ deselect is disabled in settings


tests/foreman/ui_airgun/test_architecture.py ..                          [ 28%]
tests/foreman/ui_airgun/test_os.py .....                                 [100%]

========================== 7 passed in 232.60 seconds ==========================

[oshtaier]

ACK