RBF: Secured Router should not run when it can't initialize DelegationTokenSecretManager

Currently, even if secured router fails to create DelegationTokenSecretManager, it can start and keeps running. This router can't handle requests with delegation tokens.

ERROR org.apache.hadoop.hdfs.server.federation.router.FederationUtil: Could not instantiate: ZKDelegationTokenSecretManagerImpl
...
INFO org.apache.hadoop.ipc.Server: Starting Socket Reader #1 for port 8888

In this case, I think router should not start.