Provisional workaround for router inconsistencies in background processes that switch...

Provisional workaround for router inconsistencies in background processes that switch site configs.

Ensure that router is cleared when we do site setup; we can still fetch the data from cache, so it should stay fast, but should ensure that we don't end up with someone else's routes still set up, which may be an issue breaking some of the bookmark handling that needs routing with a rare plugin.