Fix the cluster-server service definition

Looks like the cluster-server service got extra keys during editing of
the snapcraft.yaml file which went unnoticed. This change addresses
that.

Change-Id: I294b0b1e5702cb78bb5f22d01eae02e51a9056a0

snapcraft.yaml

@@ -610,8 +610,6 @@ apps:
     plugs:
       - network
       - network-bind
-    command: bin/nrpe
-    daemon: simple
 
   telegraf:
     command: bin/telegraf