KAZOO-2764: callflow module to pickup any call from any user's group

Hitting the database for each of these is a bit expensive, might I suggest collecting all the IDs in cf_pickup_any_group and issuing one DB request to get all the results at once?  Something like:

group_membership(Call, [_|_]=IDs) ->
    ViewOptions = [{'keys',  IDs}],
    ...
group_membership(Call, ID) when is_binary(ID) ->
    group_membership(Call, [ID]).