Closes-Bug: #1641411 Handle the smlite case of passing empty string f…

…or gateway value

Change-Id: Ifee5dcded8dbbf00bff20a0530e66514e73afda4

src/server_mgr_main.py

@@ -3740,8 +3740,11 @@ def get_control_ip(self, server):
     def get_control_gateway(self, server):
         control_intf = eval(self.get_control_interface(server))
         for key, value in control_intf.iteritems():
-            if 'gateway' in value and value['gateway'] != 'None':
-                return str(IPNetwork(value['gateway']).ip)
+            if 'gateway' in value:
+                if value['gateway'].isspace() or not value['gateway'] or value['gateway'] == 'None':
+                    return ''
+                else:
+                    return str(IPNetwork(value['gateway']).ip)
         if 'gateway' in server and len(server['gateway']):
             return str(IPNetwork(server['gateway']).ip)
         else: