Doing 'ad-hoc <wlan> start_open <"network name">' returned a
"No matching method found" error because start_open called
net.connman.iwd.AdHoc.Start instead of net.connman.iwd.AdHoc.StartOpen.
Station, WSC, Ad-Hoc and AP family_arg_completion functions were
identical except for which commands they were referencing and the
interface type they were interested in. Combine all these into a single
function.