Fix gdbus watch function not handling multiple dbus connections.
Fix gdbus watch function not handling multiple dbus connections.

gdbus was only adding a message filter for the very first connection given
by the user, this caused a bug in agent registration since it has a diffent
connection than previous watches it won't detect agent disappearing from the
bus.

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