Supply default username/password
In order to reduce required configuration once gitlab#216785 (closed) is closed, this MR:
- Changes
GITLAB_USER_LOGINtoTF_USERNAMEfor consistency withTF_ADDRESS - Changes
GITLAB_TF_PASSWORDtoTF_PASSWORDfor consistency withTF_ADDRESS - Supplies
GITLAB_USER_LOGINwhenTF_USERNAMEis unset - Supplies
gitlab-ci-token/CI_JOB_TOKENwhenTF_PASSWORDis unset
Relates to gitlab#216854 (closed) Relates to gitlab#216785 (closed)