We made some changes inside Review Board to upgrade the CACHES setting

during upgrade, but that neglected to handle the case where the cache

was set in siteconfig. We already had some migration logic for previous

renames, so I've just extended that to also include this new rename.

Set up a reproduction case where we had outdated CACHES configuration

  in siteconfig. Saw that I could run everything and that the

  configuration that got applied to django.conf.settings used

PyMemcacheCache. Verified that the configuration UI inside Review

  Board's admin showed the correct setting as well (was previously

  showing as "custom" when un-migrated).
Ran unit tests.