Fix issue with "usage" variable for Dynamips VMs. Fixes #1495

gns3server/schemas/dynamips_template.py

@@ -30,6 +30,11 @@ DYNAMIPS_TEMPLATE_PROPERTIES = {
         "type": "string",
         "minLength": 1
     },
+    "usage": {
+        "description": "How to use the Dynamips VM",
+        "type": "string",
+        "default": ""
+    },
     "mmap": {
         "description": "MMAP feature",
         "type": "boolean",