fix(xo-server/vm.create): allow additional props for VDIs and existingDisks

Fixes https://xcp-ng.org/forum/post/52561

packages/xo-server/src/api/vm.mjs

@@ -296,6 +296,7 @@ create.params = {
         SR: { type: 'string' },
         type: { type: 'string' },
       },
+      additionalProperties: true,
     },
   },
 
@@ -315,6 +316,7 @@ create.params = {
           optional: true,
         },
       },
+      additionalProperties: true,
     },
   },