containers: Set GITHUB_BASE in unit-tests container
containers: Set GITHUB_BASE in unit-tests container

In the unit-tests container the remote url is a file url, and the bots
try to extract the project path from this url, which fails. Avoid this
by setting the url through GITHUB_BASE.

Closes #10554

mvollmer/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,andreasn/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpit-project/cockpit,andreasn/cockpit,mvollmer/cockpit,deryni/cockpit,deryni/cockpit,andreasn/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpituous/cockpit,martinpitt/cockpit,garrett/cockpit,garrett/cockpit,martinpitt/cockpit,cockpituous/cockpit,andreasn/cockpit,cockpit-project/cockpit,deryni/cockpit,deryni/cockpit,cockpit-project/cockpit,deryni/cockpit,mvollmer/cockpit,andreasn/cockpit,andreasn/cockpit,moraleslazaro/cockpit,andreasn/cockpit,garrett/cockpit,garrett/cockpit,cockpituous/cockpit,mvollmer/cockpit,cockpituous/cockpit,garrett/cockpit,martinpitt/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,martinpitt/cockpit