Return flag for special interface that you can use in the cloud

Fix https://github.com/GNS3/gns3-gui/issues/1509

gns3server/utils/interfaces.py

@@ -205,4 +205,11 @@ def interfaces():
         if service_installed is False:
             raise aiohttp.web.HTTPInternalServerError(text="The Winpcap or Npcap is not installed or running")
 
+    # This interface have special behavior
+    for result in results:
+        result["special"] = False
+        for special_interface in ("lo", "vmnet", "vboxnet", "docker", "lxcbr", "virbr", "ovs-system", "veth", "fw", "p2p"):
+            if result["name"].lower().startswith(special_interface):
+                result["special"] = True
+
     return results