use after free in GATT scan native interface

Steps to reproduce: |-
1. Turn on BT
2. turn off BT
3. Fastpair app initiates gatt scan

Repro rate:  1/10 times

Observed result: null pointer dereference seen while accesing gattSetScanParametersNative api

Root cuase: scan native interface cleanup done before unregister DisplayListener intent.
            MSG_SCREEN_ON recieved after native interface cleanup and
            scanmanger trying to access scan native interface

Fix:  unregister DisplayListener and then cleanup scan manager

bug: 383258432
Flag: EXEMPT, trivial
Test: m Bluetooth

Change-Id: I4c4ed385cdeaabea13997dfa269f509fd32cd00c