OpenShift connector: 'getImageStreamTagFromRepo' implementation should be more robust

[ibuziuk]

After switching rhche recipes to devshift registry all stacks but vertx were broken. More details can be found in openshiftio/openshift.io#798

Basically, the problem was coupled with the fact that in getImageStreamTagFromRepo[1] method of OpenShiftConnector there was an assumption that image name would be less than 33 chars and with new registry it was not the case e.g. registry.devshift.net_che_spring-boot (Hot fix with increasing image name to 43 chars has been provided [2], but it is not ideal solution because it would still fail in future for images like registry.devshift.net_che_centos-wildfly-swarm

Some notes / ideas:

• all this image name / tag limitations are coupled with the fact that max k8s names / labels max length is 63 chars[3]
• Maybe it makes sense to limit tag size in convertPullSpecToTagName [4] (not sure but it looks like there is no real need in "che-ws-" prefix, and the size of tag itself could be limited to 12 chars. This would make k8s limitation more straight forward - 50 chars for image name : 12 chars for the tag

[1] https://github.com/eclipse/che/blob/master/plugins/plugin-docker/che-plugin-openshift-client/src/main/java/org/eclipse/che/plugin/openshift/client/OpenShiftConnector.java#L1108
[2] eclipse-che/che#6245
[3] kubernetes/kubernetes#12463 (comment)
[4] https://github.com/eclipse/che/blob/master/plugins/plugin-docker/che-plugin-openshift-client/src/main/java/org/eclipse/che/plugin/openshift/client/kubernetes/KubernetesStringUtils.java#L101

[ibuziuk]

Upstream issue - eclipse-che/che#6500

[garagatyi]

@ibuziuk I think that this issue is not relevant anymore. There is no OpenshiftConnector in Che 6. Can we close this issue?

[ibuziuk]

yeah, let's close it as outdated