software/{kvm,theia}: fix $ref in json schema

Fixes this warning when running test:

    UserWarning: Error validating request parameters against schema definition:
    RefResolutionError unknown url type: 'instance-input-schema.json'

jsonschema (the python library) support this kind of refs when using
version draft-06 but not when using draft-04.

json-language-features (from theia text editor) does not understands
file.json#/ references, it complains:

    $ref '/' in 'file://...' can not be resolved.(768)

but not using the trailing / works fine

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

 {
   "type": "object",
-  "$schema": "http://json-schema.org/draft-04/schema",
+  "$schema": "http://json-schema.org/draft-06/schema",
   "allOf": [
     {
-      "$ref": "instance-kvm-input-schema.json#/"
+      "$ref": "./instance-kvm-input-schema.json#"
     },
     {
       "properties": {

software/theia/instance-input-schema.json

 {
-  "$schema": "http://json-schema.org/draft-04/schema#",
+  "$schema": "http://json-schema.org/draft-06/schema",
   "type": "object",
   "description": "Parameters to instantiate Theia",
   "additionalProperties": false,

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

 {
-  "$schema": "http://json-schema.org/draft-04/schema",
+  "$schema": "http://json-schema.org/draft-06/schema",
   "type": "object",
   "description": "Parameters to instantiate resilient Theia",
   "allOf": [
     {
-      "$ref": "instance-input-schema.json#/"
+      "$ref": "./instance-input-schema.json#"
     },
     {
       "properties": {