[fprint] AES2501 state confusion

[Daniel Drake]

Philippe Troin wrote:
>  - I type my login
> 
>  - I do an incorrect swipe with the tip of my finger.
> 
>  - fprint asks: "Place your finger on the reader again".
> 
>  - Now, whatever I do, even if I swipe my finger at the normal speed,
>    fprint will always ask "Place your finger on the reader again".
> 
> This is where my lack of understanding kicks in:  it looks like
> start_capture is called with leftover action_state and action_result
> from the previous incorrect swipe, and that prevents any further swipe
> from being accepted.


The async API is a bit sensitive to being run in an intended, 
undocumented order :) maybe this is the problem.

Can you reproduce this with fprint_demo? (the git version, which uses 
the async API)

Daniel