Handle wakelocks for device connection intents from AudioService

Now that AudioService handles the device connection intents itself,
 those need to be sent under wakelock.
 The wake lock is acquired when AudioService is notified of the
 device connection, and released when the corresponding message
 has been handled.
This change only covers the device connection messages, and doesn't
 affect the handling of the other AudioService messages.

Bug 6485897

Change-Id: I2d35f5404f097b5adde8af21fd81347bdd5576a6