In some cases, when the device is already connected there's no need
to create another GAttrib instance.
This will allow the Attrib client to use the connection already
estabilished, this will be very useful when we support more
LE profiles.
Now that Attrib client is being moved to the core, there's no
need to have explicit _init and _exit methods.
This also means that we need to pass the DBusConnection explicitly
to the registration method.
Contains device driver declaration for attribute protocol. Registers
D-Bus path/interface to represent the remote device client: BR/EDR or
LE. For the most common LE scenarios, devices running BlueZ will be
client role.
