Make dicts_of_dicts test use conversion trait
Make dicts_of_dicts test use conversion trait

Signed-off-by: David Henningsson <9fb354e0a5603a0331399c18f4aa5aab2f9d9c5b@canonical.com>

gemmarx/dbus-rs,mathstuf/dbus-rs,manuels/dbus-rs