Only perform fencing duties on primary

There was really no need for this to be shared among all the
coordinators, which seemed more fragile. This way only the primary will
try to fence dead nodes.

node-daemon/pvcd/Daemon.py

@@ -1120,7 +1120,8 @@ def update_zookeeper():
         # Close the Libvirt connection
         lv_conn.close()
 
-    # Look for dead nodes and fence them
+    # Look for dead nodes and fence them (primary only)
+    if this_node.router_state == 'primary'
         if debug:
             print("Look for dead nodes and fence them")
         if config['daemon_mode'] == 'coordinator':