Hearing Aid: Removes all registrations for connection when disconnect HA

* On the current design, when the disconnect Hearing Aid is triggered
from UI. It will Cancel autoconnect by gatt_if first. It will cause the
fixed_chnl_idle_tout isn't set. On the condition, it will cause the
disconnect isn't finished.
* The fix is change the behavior. Directly remove all registrations for
connection when disconnect HA.

Bug: 122264537
Bug: 123214035
Test: make, BT off/on when connected HA,
Toggle disconnect/connect HA from Bluetooth UI,
Turn off/onn HA after Connected HA.

Change-Id: If011c1ab632e1fcb51a68b3c122743534b5f6c63