SCT + siren-tests integration, validate multiDC setup

[mikliapko]

It has been verified that SCT + siren-tests integration is fully functional for singleDC cluster (both AWS and GCE).

The next step is to confirm the same but for multiDC cluster.

Currently, siren-tests supports multiDC cluster deployment (see some multiDC cluster jobs here) as well as SCT supports test execution against multiDC cluster setup. The only thing, such kind of integration running SCT tests against multiDC siren cluster has not been tested before.

Test frameworks might be missing some part allowing such an integration to work.
That's what should be verified in of this task.