driver pod not handle some executor pod fail

[ChenLingPeng]

If an executor pod failed before register to the driver, the driver can't aware these executors and can't create a new executor.

e.g.
the pic below shows an exception before register to the driver, which is raised by CoarseGrainedExecutorBackend.askAsync

the driver expects the executor to register but not handle the failed executor, the log below shows that

the reason is that when watch executor, we have not handle the failed executor event which is Action.MODIFY and in Failed phase.

I will pull a request to fix this