Discard time-sync for some envs

If env is not Fuel, we can't know slaves IPs,
that is why we should not start time-sync procedure.

Change-Id: I15770841ee1c886544cc734ee1ff1674ce2aa3af
Closes-Bug: 1609006

devops/shell.py

@@ -159,6 +159,9 @@ class Shell(object):
             print(' '.join(slave_ips))
 
     def do_time_sync(self):
+        if not self.env.has_admin():
+            print('There is no FuelAdmin node. It is impossible to sync time')
+            return
         node_name = self.params.node_name
         node_names = [node_name] if node_name else None
         cur_time = self.env.get_curr_time(node_names)