Since now wifi interface proxy is created async in Wifi (the only
inheriting class), calling _refresh from _start() could easily mean that
location query is created while we don't have an interface (or list of
BSS proxies, which are also created async) and end-up making a
geoip-only query to the server. Also we can easily end-up not making the
wifi query at all if geoip-only query is still in process since we only
allow one query at a time.

Let's leave this to subclasses (we only have 1 right now anyway).