fix(driverBench): driverBench has default options object now

Author: daprahamian

test/mongoBench/runner.js

@@ -68,6 +68,7 @@ const Suite = require('./suite');
 
 class Runner {
   constructor(options) {
+    options = options || {};
     this.minExecutionTime = options.minExecutionTime || CONSTANTS.DEFAULT_MIN_EXECUTION_TIME;
     this.maxExecutionTime = options.maxExecutionTime || CONSTANTS.DEFAULT_MAX_EXECUTION_TIME;
     this.minExecutionCount = options.minExecutionCount || CONSTANTS.DEFAULT_MIN_EXECUTION_COUNT;