connman-usb-tethering dialog issue

connman-test-service.py script is not handling the issue when the ethernet technology is not enabled,
it shows the dialog error and stops.

Fix: Added check if no interface is available.

Apertis: T5931

Signed-off-by: Tarun Baghmar <tarun.baghmar@in.bosch.com>

connman/connman-test-service.py

@@ -210,6 +210,10 @@ if __name__ == "__main__":
                              "net.connman.Manager")
 
     services = manager.GetServices()
+    
+    if len(services) == 0 :
+       print "Error: Ethernet Interface not enabled"
+       exit(1)
     options = {}
     for path, props in services:
         identifier = path[path.rfind("/") + 1:]