[floss] Fix garbage disconnecting state metric

Previously, an incorrect variable was used to provide the address of a
disconnecting peripheral, producing a garbage value for the
peripheral's address.

This change uses the correct variable to fetch the actual address of a
disconnecting peripheral.

Bug:264969525
Test: Ensure disconnecting state address is correct when turning off \
a Bluetooth connected peripheral

Change-Id: I7e80d637c69f8ae838ebef4db6f0d4936e210085