Shutdown/cleanup cluster extension if actor init fails, see #3162

* Stop ClusterDaemon if init of core actor fails.
* Activate jmx-enabled setting
* Adjust the err msg of InvalidActorNameException to match conventions
Merge pull request #1261 from akka/wip-3162-cluster-cleanup-init-patriknw

Shutdown/cleanup cluster extension if actor init fails, see #3162