Add ability to specify environment variables to the docker run
Towards #26 (closed), we add the ability to specify environment variables such as GITLAB_OMNIBUS_CONFIG
via a new Gitlab::QA::Docker::Gitlab#environment accessor, which accepts a hash of environment variables.
May address all or some of the need expressed in #72 (closed)
For an example of this feature in use see this scratch commit: https://gitlab.com/richardc/gitlab-qa/commit/00d1464803e727e309d7bcc2ab3deb747b6ca42b
Edited by George Koltsov