PEP8 (make qa) fixes for web/cobbler_web/views.py

web/cobbler_web/views.py:190:28: E711 comparison to None should be 'if cond is not None:'
web/cobbler_web/views.py:299:13: E711 comparison to None should be 'if cond is None:'
web/cobbler_web/views.py:448:17: E711 comparison to None should be 'if cond is None:'
web/cobbler_web/views.py:471:17: E711 comparison to None should be 'if cond is None:'
web/cobbler_web/views.py:494:17: E711 comparison to None should be 'if cond is None:'
web/cobbler_web/views.py:1077:17: E711 comparison to None should be 'if cond is not None:'
web/cobbler_web/views.py:1089:8: E714 test for object identity should be 'is not'
web/cobbler_web/views.py:1133:12: E713 test for membership should be 'not in'
web/cobbler_web/views.py:1239:22: E711 comparison to None should be 'if cond is not None:'