We stopped writing pickled rings more than twelve years ago. Any
cluster that was going to upgrade from then has, or can pick any of
the multitude of intermediary releases to pause at and push rings.
We can also safely assume that regions will be present for devices;
that change is nearly as old.
As a side-effect, clean up some old tests that did nonsense things
like having 7 assignments per row for a part-power-2 ring.
UpgradeImpact: remove ability to read rings written by swift <1.7.0
circa 2012
Related-Change: I799b9a4c894d54fb16592443904ac055b2638e2d
Related-Change: Ifefbb839cdcf033e6c9201fadca95224c7303a29
Signed-off-by: Tim Burke <tim.burke@gmail.com>
Change-Id: Ic8322b18d51b40f586cb217a0d1b2f345e1d8df6
0417979ca5