Use lambdas instead of slots where practical.
Consistently use signals to transmit D-Bus messages.
Extract a local variable for the used D-Bus connection.
Task-number: QTBUG-111366
Pick-to: 6.5
Change-Id: Icc6667e1392ada1b7d3b33c4e4b32917dd648390
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
742e79312f