b/2314560 Prevent PIN dialog from showing up on undocked docks

If unpaired while undocked, device will be removed from the BT device list.
If unpaired while docked, the user can do pair and connect. No PIN dialog will pop up.
If undocked after unpaired, device will be removed from the BT device list.

Change-Id: Id587a517999e08641451f78dec8696a06028cf16