Manage GAttrib refs based on registered callbacks
Manage GAttrib refs based on registered callbacks

Connection should not be dropped if there is at least one ATT connection
callback registered. After discovering primary services over the LE link,
GAttrib ref needs to be held to allow notifying an active connection
while registering connection callbacks(inside plugins probing).

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