Read paired device After LocalBtManager is created

After this cl, it could guarantee that device list always has
saved devices:
1. Even though in onCreate(Fix flaky UI)
2. Even though there is no other bluetooth event to trigger it
(e.g. no device is connecting)

Fixes: 70934171
Fixes: 63910184
Test: Build
Change-Id: Iec628d455690a68d92f201f6eac9cd97b555b2b4