core/gatt-client: fix losing notifications

core/gatt-client: fix losing notifications

When notifications are quickly send to BlueZ, it tries to signal that
through dbus using g_dbus_emit_property_changed, which would merge all
changes and schedule sending property changed in g_iddle_add.

If the stream of notifications from device is fast enough, there might be
no iddle moment to send properties changed before next notification
arives, which would result in notifications being lost.

This patch fixes that by using method that sends properties changed
immediately, without waiting for iddle moment.