kvm: Fix resilient json schema

software/kvm/instance-kvm-resilient-input-schema.json

 {
     "type": "object",
     "$schema": "http://json-schema.org/draft-04/schema",
-    "items": {
     "allOf": [
         {
-                "$ref": "instance-kvm-input-schema.json"
-            }
-        ],
-        "title": "Input Parameters",
+            "$ref": "instance-kvm-input-schema.json#/"
+        },
+        {
             "properties": {
                 "-sla-0-computer_guid": {
                     "title": "Target computer for main instance",
                     "description": "Target computer GUID for main instance.",
-                "type": "string"
+                    "type": "string",
+                    "optional": true
                 },
                 "-sla-1-computer_guid": {
                     "title": "Target computer for first clone",
                     "description": "Target computer for first clone and PBS.",
-                "type": "string"
+                    "type": "string",
+                    "optional": true
                 },
                 "-sla-2-computer_guid": {
                     "title": "Target computer for second clone",
                     "description": "Target computer for second clone and PBS.",
-                "type": "string"
+                    "type": "string",
+                    "optional": true
                 },
                 "resiliency-backup-periodicity": {
                     "title": "Periodicity of backup",
                     "description": "Periodicity of backup, in cron format.",
-                "type": "string"
+                    "type": "string",
+                    "optional": true
                 },
                 "remove-backup-older-than": {
                     "title": "Remove backups older than...",
                     "description": "Remove all the backups in PBS that are older than specified value. It should be rdiff-backup-compatible.",
                     "type": "string",
-                "default": "3B"
+                    "default": "3B",
+                    "optional": true
                 },
                 "resilient-clone-number": {
                     "title": "Amount of backup(s) to create",
                     "description": "Amount of backup(s) to create. Each backup consists of a Pull Backup Server and a clone.",
                     "type": "integer",
-                "default": 2
+                    "default": 2,
+                    "optional": true
                 },
                 "ignore-known-hosts-file": {
                     "title": "Ignore known_hosts file",
                     "description": "Set either to fill known_hosts file for ssh or not. Useful if main instance and PBS are using the same IP (slapos proxy, webrunner).",
                     "type": "boolean",
-                "default": false
+                    "default": false,
+                    "optional": true
                 }
             }
         }
+    ]
 }