floss: LE scan: Set FilterDuplicates enabled

BlueZ enables FilterDuplicates while Android (Floss) doesn't.
Since a performance drop is observed when switching from BlueZ to Floss,
enable it to mimic the original behavior.

Bug: 315276614
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: SmartLock, PhoneHub, and NearbyShare
Test: bluetooth_AdapterLEHealth.all_floss \
      bluetooth_AdapterAdvMonitor.all_floss
Flag: EXEMPT floss only changes
Change-Id: I985162a3d4726024328191099c34030995c036fd