Get rid of local copy of cmdln.py

Get rid of local copy of cmdln.py

In the current code thereis a copy of cmdln.py module, which is also
present in osc. gbs depends on osc, so it's better to just use cmldn
from there to avoid unneeded code duplication.

Change-Id: Ib3301ad1635ac681e7b7213aafa17bed0ac22c0a