ci/b2c: add support for the new format of CI_RUNNER_TAGS

Seems like Gitlab did not follow their own documentation:

CI_RUNNER_TAGS  8.10  0.5  A comma-separated list of the runner tags.

But it would seem like a gitlab update brought json-style lists which broke:

CI_RUNNER_TAGS = '["keywords-gateway", "CI-gateway"]'

This commit adds support for both style.

Signed-off-by: Martin Roukala (né Peres) martin.roukala@mupuf.org