Broadcast ACTION_NETWORK_STATS_UPDATED in NetworkStatsHandler

There is a corner case which may cause the deadlock:
When NetworkStatsService tried to broadcast the intent,
NetworkStatsService was waiting for a lock which was hold by
ActivityManagerService. In the same time, ActivityManagerService
was waiting for ActiveService#startServiceInnerLocked() to get a
lock which was hold by ConnectivityService. ConnectivityService
was waiting for a lock which was hold by BatteryStatsImpl.
BatteryStatsImpl was waiting for a lock which was hold by
NetworkStatsService, and the lock was locked by
NetworkStatsService when NetworkStatsService tried to broadcast
the intent.

To prevent deadlock when broadcasting the intent in
performPollLocked(), move the intent broadcasting from
performPollLocked() to NetworkStatsHandler.

Bug: 150418178
Bug: 155155473
Test: 1. Create the second user and see if the device will
         do factory reset or not.
      2. Factory reset manually and see if there is a deadlock.
Change-Id: Icf88d3e7a38562ab15187f6c71bc8fb0486d37c0