gitlab-ci: Move trace backend tests across to gitlab

Similarly to commit 8cdb2cef, move the trace backend
tests to GitLab.

Note the User-Space Tracer backend is still tested on
Ubuntu by the s390x jobs on Travis-CI.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201111121234.3246812-3-philmd@redhat.com>
Message-Id: <20201117173635.29101-7-alex.bennee@linaro.org>