tests/qtest/ipmi-bt-test: Zero-initialize sockaddr struct

tests/qtest/ipmi-bt-test: Zero-initialize sockaddr struct

Zero-initialize the sockaddr_in struct that we're about to fill in
and pass to bind(), to ensure we don't leave possible
implementation-defined extension fields as uninitialized garbage.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-id: 20210813150506.7768-4-peter.maydell@linaro.org