Detect default project branch for scenarios
Follow-up on !350 (merged)
GitLab ignores default_branch
param when creating a project via API - gitlab-org/gitlab#26261 (closed). To support both 13.x and 14.x versions due to the change of the default branch in gitlab-org/gitlab!62467 (merged), we need to detect which branch is the default and pass it to scenarios.
Tested this change against 13.13.0-pre 48b385ebb2c
where the default branch is master
and against 14.0.0-pre 4acff819b84
with the main
default branch.