configure_edison - fix console password inputs

[mwallnoefer]

The O_NONBLOCK terminal attribute settings didn't work reliably.
But we may do without it using buffer flushing instead.

[htot]

Before applying this patch I tried configure_edison --wifi, the issue does not occur, however password is visible while typing.
I also did configure_edison --password, and indeed the issue happens, both from serial console and ssh tty.

Do I understand correct both cases are fixed by this patch?

[mwallnoefer]

Yes, both cases are fixed by this commit.

On configure_edison --wifi I once had disabled the password input function by instead using the plain input one, but then completely forgotten to fix it properly.

[htot]

Merged, thanks!