Run downstream pipeline on unreleased OCP version (e.g. candidate release)

4.17 was RC during the release but it got into GA before our release, so we tested with 4.17 GA and 4.18-ec1 in this task:

4.17GA :

smcp	status
2.6
2.5
2.4

Polarion

4.18 ec1 Polarion * TestIstioCsr/TestPluginCaCert failed since cert-manager is not available in the OperatorHub on the OCP 4.18 ec1 yet