Fix gatt_is_bda_in_the_srv_chg_clt_list always return NULL

This function always return NULL. The error prevents server
from sending an indication to client when services is changed
on the server.

Change-Id: I0472baa805b339a062c63f498f3ad9271d7e5701
Test: PTS7.1.1 GATT/SR/GAS/BV-01-C