refactor: put recovery tokens behind a feature flag for now

Author: mbroadst

lib/operations/mongo_client_ops.js

@@ -111,7 +111,8 @@ const validOptionNames = [
   'retryWrites',
   'useNewUrlParser',
   'useUnifiedTopology',
-  'serverSelectionTimeoutMS'
+  'serverSelectionTimeoutMS',
+  'useRecoveryToken'
 ];
 
 function addListeners(mongoClient, topology) {

test/functional/transactions_tests.js

@@ -324,6 +324,7 @@ function runTestSuiteTest(configuration, spec, context) {
   // test-specific client optionss
   clientOptions.autoReconnect = false;
   clientOptions.haInterval = 100;
+  clientOptions.useRecoveryToken = true;
 
   const url = resolveConnectionString(configuration, spec);
   const client = configuration.newClient(url, clientOptions);