suzerain: #3020 "radial_nozzle" -> "radialflow"

Recent work means we can do nozzles and diffusers just
the same, so shorten the common token prefix accordingly.

THIS WILL BREAK RESTART FILES THAT CONTAINED BASEFLOW INFORMATION
(but there aren't any of any value yet so no compatibility provided).

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43174 0bd85f0b-c151-43b9-a1e9-27231104551f