Set a flag on login to remember that the device needs to be verified
so that we don't forget if the user refreshes the page, but still allow
user with an existing unverified session to stay logged in.

Much, much tweaking to make the matrixchat tests pass again. Should
hopefully make them a bit more solid in general with judicious use of
waitFor rather than flushPromises(). Also lots of fun to stop the state
bleeding between tests.

to hopefully resolve infinite package sadness

Mock out the createClient method to return the same client, because
we've mocked the peg to always return that client, so if we let the
code make another one having still overridden the peg, everything becomes
cursed.

Also mock out the autodiscovery stuff rather than relying on fetch-mock.

Actually it breaks all sorts of other things too, having fixed all the
MatrixChat tests (although this is useful anyway).

but move ready transition to avoid flash of main UI

or in one case just await it because the caller was async anyway