Bluetooth: Unregister servers for BLE_ON to ON switch

This change unregisters all the server apps and thus
all the services registered at the BLE ON state.
This is in line with the unregister of all the clients
when the adapter state is switched from BLE_ON to ON
state.

Change-Id: Ifaf7050c2c70c78347a5e92fcda75124ed2c8f2c
CRs-Fixed: 1079098