🔧 Move docker_setup role application to group playbook

To install docker on a host you have to put it into that group in
inventory now, instead of adding the role to each host playbook.  Idea
is to extend the group docker_host playbook by more docker related
things as for example metrics and monitoring.

main.yml

@@ -7,6 +7,9 @@
 - name: Specific setup for all proxmox hosts
   import_playbook: group-proxmox.yml
 
+- name: Specific setup for all docker host hosts
+  import_playbook: group-docker_host.yml
+
 - name: Tau specific setup
   import_playbook: host-tau.yml