Option --no-beep is added to mysqladmin like it already exists in
the "mysql" command-line client (short option: -b; long: --no-beep).
Default is to emit beeps like that "mysql" client.
Can't test in the testsuite; but on my Linux I tested by hand:
open a *xterm* and there do "mysqladmin shutdown" - I hear a beep;
with --no-beep, no beep.