Git auth failure can cause QA CI jobs to timeout without showing output

Sometimes QA jobs will timeout without showing much output, e.g.: https://gitlab.com/gitlab-org/quality/staging/-/jobs/135334372

Running test suite `Test::Instance` for gitlab-ee
Docker shell command: `docker run -t --rm --net=bridge --env GITLAB_USERNAME="$GITLAB_USERNAME" --env GITLAB_PASSWORD="$GITLAB_PASSWORD" --env GITLAB_FORKER_USERNAME="$GITLAB_FORKER_USERNAME" --env GITLAB_FORKER_PASSWORD="$GITLAB_FORKER_PASSWORD" --env GITLAB_QA_ACCESS_TOKEN="$GITLAB_QA_ACCESS_TOKEN" --env GITHUB_ACCESS_TOKEN="$GITHUB_ACCESS_TOKEN" --env GCLOUD_ACCOUNT_EMAIL="$GCLOUD_ACCOUNT_EMAIL" --env GCLOUD_ACCOUNT_KEY="$GCLOUD_ACCOUNT_KEY" --env GCLOUD_ZONE="$GCLOUD_ZONE" --env SIGNUP_DISABLED="$SIGNUP_DISABLED" --env QA_DEBUG="$QA_DEBUG" --env QA_LOG_PATH="$QA_LOG_PATH" --env QA_CAN_TEST_GIT_PROTOCOL_V2="$QA_CAN_TEST_GIT_PROTOCOL_V2" --env GITLAB_QA_PASSWORD_1="$GITLAB_QA_PASSWORD_1" --env GITLAB_QA_PASSWORD_2="$GITLAB_QA_PASSWORD_2" --volume /var/run/docker.sock:/var/run/docker.sock:z --volume /builds/gitlab-org/quality/staging/gitlab-qa-run-2018-12-17-04-26-14-724d5b43/gitlab-ee-qa-db0a1551:/home/qa/tmp:z --name gitlab-ee-qa-db0a1551 dev.gitlab.org:5005/gitlab/omnibus-gitlab/gitlab-ee-qa:11.6.0-rc7-ee Test::Instance https://staging.gitlab.com qa/specs/features/browser_ui/3_create`
Pulling docker image gitlab/gitlab-runner-helper:x86_64-3afdaba6 ...
ERROR: Job failed: execution took longer than 1h0m0s seconds

In the past the cause turned out to be git authentication failure. E.g.: https://gitlab.com/gitlab-org/quality/nightly/issues/28 and https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8721

The authentication failures have been fixed, but it would be helpful if we could fix the lack of up-to-date output.

I suspect the job is waiting for input (i.e., a password) and somehow that interferes with capturing and displaying the output. It might be related to executing the git command from inside a docker container.

Note that if the same docker container is launched locally execution stalls at the same point, but the output is displayed.