Refactor: call find_site_by_name just once, up the stream

Respective logic was duplicated for all "booth list/peers/grant/revoke"
and "geostore list/get/set/del" separately, so utilize a natural control
flow to carry this once-resolved target site from here, sharing it with
the special case of "daemon" role invoked with "-s site" (debug mode).
Side effect: simpler, terser code.