Update RestfulServer.java

I believe that in line 538 you are falsely assuming that multiple _* parts in the path could not happen. As of DSTU2 there's _meta/_delete. Unfortunately the DSTU for Comment erroneously lists _meta-delete.

hapi-fhir-base/src/main/java/ca/uhn/fhir/rest/server/RestfulServer.java

@@ -535,6 +535,7 @@ public class RestfulServer extends HttpServlet {
 						operation = Constants.PARAM_HISTORY;
 					}
 				} else if (nextString.startsWith("_")) {
+					//FIXME: this would be untrue for _meta/_delete
 					if (operation != null) {
 						throw new InvalidRequestException("URL Path contains two operations (part beginning with _): " + requestPath);
 					}