Fix timing issues in RCTLoggingTests.m

Summary:
**Motivation**

If there are any console log messages that come in on initialization (as will happen right now in tvOS), the RCTLoggingTests can fail intermittently.  This change delays the start of the logging test to allow time for initial console messages to come in.
Closes https://github.com/facebook/react-native/pull/10568

Differential Revision: D4087974

Pulled By: bestander

fbshipit-source-id: 2b0f4a88a74bc6121133317dd909d5bd1f10789b

IntegrationTests/LoggingTestModule.js

@@ -19,6 +19,11 @@ var LoggingTestModule = {
   logToConsole: function(str) {
     console.log(str);
   },
+  logToConsoleAfterWait: function(str,timeout_ms) {
+    setTimeout(function() {
+      console.log(str);
+    }, timeout_ms);
+  },
   warning: function(str) {
     warning(false, str);
   },