Show the test coverage if it is available
What does this MR do?
It will just show the build/pipeline test coverage when it is available, and not just only when it is enabled.
Why was this MR needed?
Because in some cases there was a coverage to present, but not presented due to settings.
Screenshots
What are the relevant issue numbers?
Closes gitlab-org/gitlab-ce#27911
Issue gitlab-org/gitlab-ce#25424 should take care of showing the coverage in the merge widget.