Text is being echoed before the prompt is ready

[rnhmjoj]

Unfortunately I have a rather slow prompt (can take >250ms) and it happens that I start typing text into the shell before the prompt is ready. This hasn't been an issue since fish would just delay the echo for a moment, until the prompt is printed.
Starting from 2a3677b, however, at least part of the text is printed immediately and duplicated:

This is not a big deal but it's a bit ugly. Is there something I can do (besides optimising the prompt) to revert to the previous behavior?

cc: @faho

[rnhmjoj]

For the moment I came up with this:

function fish_greeting
  clear
end

It's not perfect because sometimes the text is still not cleared but it's something.

[ridiculousfish]

Let's move the call to set the tty to shell modes above the call to fish_prompt. This will make the prompt run with shell modes, but I feel confident in that change, because that's how fish worked prior to 2a3677b. Thanks for filing!