Abort connecting to native daemon during shutdown

Symptom:
System_server crashed due to unsolved "netd" service.

Root cause:
Init intentionally killed services when shutdown was triggered.
NativeDaemonConnector unnecessarily tried to reconnect the killed
daemon and NetworkManagemantService got a callback of connection.
Finally, NetworkManagemantService failed to get netd service and it
crashed with NPE.

Solution:
Do not retry connecting to the target native daemon when the device
is in the middle of shutdown.

Bug: 64237349
Change-Id: I2514cdc47b3eea785b5ffe5bd8bb27609bcc1726