android/gatt: Fix matching characteristic
android/gatt: Fix matching characteristic

This patch fixes searching for characteristic within service.
Characteristics should be matched by element id (uuid, instance) not
only instance id. Also redundant helper to match characteristic by
instance is removed.

pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,ComputeCycles/bluez,pkarasev3/bluez,mapfau/bluez,silent-snowman/bluez,ComputeCycles/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,mapfau/bluez,silent-snowman/bluez,ComputeCycles/bluez,silent-snowman/bluez,silent-snowman/bluez