Bug 1316622 - Make implicit wait timeout default to 0; r=automatedtester

The WebDriver specification mandates that the implicit wait timeout should
default to 0 (off), which in Marionette has the same effect as null.

MozReview-Commit-ID: Ca3RxO7gHv8

--HG--
extra : rebase_source : 5a804614b0bdf99c7d1241bbc06f3566f127b32f

testing/marionette/driver.js

@@ -110,7 +110,7 @@ this.GeckoDriver = function(appName, server) {
   this.curBrowser = null;
   this.context = Context.CONTENT;
   this.scriptTimeout = 30000;  // 30 seconds
-  this.searchTimeout = null;
+  this.searchTimeout = 0;
   this.pageTimeout = 300000;  // five minutes
   this.timer = null;
   this.inactivityTimer = null;