In a fresh VM, following the instructions in
https://wiki.apertis.org/QA/Test_Cases/bluez-phone


means that the device object has not yet been created, fiddling
with d-feet showed me that `StartDiscovery` was necessary for this
to happen, which is called by scan_for_device.

The result was an enigmatic D-Bus error message:

Create device failed org.freedesktop.DBus.Error.UnknownObject: Method
"Pair" with signature "" on interface "org.bluez.Device1" doesn't exist

which is solved with this patch.

Reviewed-by: Philip Withnall <philip.withnall@collabora.co.uk>
Signed-off-by: Mathieu Duponchelle <mathieu.duponchelle@opencreed.com>
Differential Revision: https://phabricator.apertis.org/D4264