[SPARK-4498][core] Don't transition ExecutorInfo to RUNNING until Driver adds Executor

The ExecutorInfo only reaches the RUNNING state if the Driver is alive to send the ExecutorStateChanged message to master.  Else, appInfo.resetRetryCount() is never called and failing Executors will eventually exceed ApplicationState.MAX_NUM_RETRY, resulting in the application being removed from the master's accounting.

@JoshRosen