Add Test::Integration::Mattermost to qa:test
Part of gitlab-qa#26 (closed); we added a new suite to gitlab-qa to test if enabling Mattermost would break the rest of the flow. Here we add this test to the omnibus-gitlab pipeline.
Part of gitlab-qa#26 (closed); we added a new suite to gitlab-qa to test if enabling Mattermost would break the rest of the flow. Here we add this test to the omnibus-gitlab pipeline.