A network's QoS form whose rate was not a whole number (abc, 1.5) made
wvmNetwork.set_qos raise a ValueError that the view did not catch: the
request ended in a server error. The page's pattern stops this in a
browser, but the server must refuse it too. set_qos now says "QoS rates
must be whole numbers", and the view reports that, as it does a libvirt
error, and goes back to the network's page.
