Cloudera app: startServices etc in start() rather than in main()

- so works with `brooklyn launch`, through catalog
Fix worker-node managedHostId

- prefer LOCAL_HOSTNAME (if it's set and matches MANAGED_HOSTS entry)
Expose ClouderaService.create as effector
Bootstrapper: disable port_mapper

- changed DNAT in vcloud vorg to use 8081, so mapper not needed
- TODO delete rather than comment out!
cdh-manager selinux: workaround when disabling

- because reboot can reset the /etc/resolv.conf which may have been
  set for internal DNS, ensure that we only allow internal-dns to be
  triggered after reboot.