Change ClusterMap API object to support multiple kubeconfig sources
for a cluster. If one kubeconfig source fails, kubeconfig builder
will not fail and move on to the next one. This behaviour will allow
to support cases when ephemeral cluster is not accesible anymore or
when target cluster is not yet accessible.
For more information please read issue #460 in airshipctl github
Relates-To: #460
Related-To: #460
Change-Id: I7cd32f78cd7c4ad8814eac357424c24216f40d76
6207e2c24d