Ensure redirection to path with .git suffix regardless whether project
exists or not.

As mentioned in
https://gitlab.com/gitlab-org/gitlab-ee/issues/9035#note_129093444,
Rails 5 switched ActionDispatch::Request so that it no longer inherits
Rack::Request directly. A middleware that uses Rack::Request to
read the environment may see stale request parameters if
another middleware modifies the environment via ActionDispatch::Request.
To be safe, we should be using ActionDispatch::Request everywhere.

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

Before the push git would make a call to
`/:namespace/:project/git-receive-pack`. This would perform an access
check without a ref. So the `Project#branch_allows_maintainer_push?`
would return false.

This adjusts `Project#branch_allows_maintainer_push?` to return true
when passing no branch name if there are merge requests open that
would allow the user to push.

The actual check then happens when a call to
`/api/v4/internal/allowed` is made from a git hook.

Allow builds that have been triggered by a user before terms were
enforced access to git. That way the builds can complete as usual.