Bug 978809: Remove sToggleBtMonitor from Bluedroid backend, r=echou

When enabling or disabling Bluetooth, the Bluedroid backend waits
on sToggleBtMonitor until a BT adapter has been activated. Once
the monitor gets notified, the backend sends a ToggleBtAck runnable
to the main thread.

This patch removes sToggleBtMonitor from the Bluetooth Bluedroid
backend. Instead of signalling the monitor's notification, the
Bluedroid handler function sends the ToggleBtAck directly.
Bug 978809: Send ToggleBtAck after finishing BlueZ connection setup, r=echou

With this patch, ToggleBtAck is sent by the BlueZ backend of
Bluetooth after the connection has been set up completely.