Remove openstack-common.conf
Remove openstack-common.conf

This commit removes openstack-common.conf file. It was introduced by the
cookiecutter when the os-testr repository was created. However, this
file isn't used anymore, and it was already removed from the
cookiecutter repository as a cleanup[1].

[1] I2b5377391a4422caa395f62fbd5df3049f01fdec

Change-Id: Id33e4c7c4bd8cebded08f5dad55a60cf0be7cd0f

openstack/os-testr