remove Pan service which is not used anymore.

because we replaced bluez bluetooth stack with bluedroid bluetooth stack.
This is multiple project check-in for ISSUE 6849488 Bluedroid stack, remove system/bluetooth.
Pan service depend on system/bluetooth. So both Pan service and system/bluetooth should be removed.

bug 6849488

Change-Id: I7a5a828b9b4327dbd6b6a13ec7ff4a9129ba0ca5