Fixed http method one exist API

src/main/java/org/gcube/informationsystem/resourceregistry/schema/ResourceRegistrySchemaClientImpl.java

@@ -103,7 +103,7 @@ public class ResourceRegistrySchemaClientImpl implements ResourceRegistrySchemaC
 			parameters.put(TypePath.POLYMORPHIC_PARAM, Boolean.FALSE.toString());
 			gxHTTPStringRequest.queryParams(parameters);
 			
-			HttpURLConnection httpURLConnection = gxHTTPStringRequest.get();
+			HttpURLConnection httpURLConnection = gxHTTPStringRequest.head();
 			HTTPUtility.getResponse(String.class, httpURLConnection);
 			
 			return true;