Increase default label limit for BaseExplorer

Right now limit is set to 60, but a lot of cluster names generated by CI are quite long(for example: https://api.ci-ln-xggszgk-f76d1.origin-ci-int-gce.dev.openshift.com:6443) so the cluster name is shortened:

But this shortened label is not very user friendly and it also make testing with automated tests much harder.