fixes #6430 - validate presence of location and organization for managed host if Settings are turned on

Perhaps we should do both then?  I think having `:required` or the param appear/disappear is useful for Hammer to dynamically tell users if it's needed or not.

It might actually be preferable to do this:

    param :location_id, :number, :desc => "if locations are enabled", :required => true if SETTINGS[:locations_enabled]

Then the docs have a user-friendly comment, plus Hammer then gets dynamic behaviour depending on the server configuration.