Edebug: avoid messages on 'f' command

[Paul Pogonyshev]

In Edebug 'f' is bound to 'edebug-forward-sexp'. It can be seen as
"faster" space key, allowing you to step through function a whole sexp
at a time. However, there is an annoyance to it: each time I hit it,
echo area displays "Break" for about a second, which is only then
replaced by "Result: ...". By comparison, space displays result
immediately.

Request: improve Edebug to not print such intermediate message(s)
during 'f' and similar commands.

Paul