util/qemu-sockets.c: Avoid unused variable warnings

The 'on' variable is never used, and 'off' is only used
if IPV6_V6ONLY is defined; delete 'on' and move 'off' to
the point where it is used. This avoids warnings from
clang 3.4.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

util/qemu-sockets.c

@@ -30,8 +30,6 @@
 # define AI_ADDRCONFIG 0
 #endif
 
-static const int on=1, off=0;
-
 /* used temporarily until all users are converted to QemuOpts */
 QemuOptsList socket_optslist = {
     .name = "socket",
@@ -159,6 +157,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp)
 #ifdef IPV6_V6ONLY
         if (e->ai_family == PF_INET6) {
             /* listen on both ipv4 and ipv6 */
+            const int off = 0;
             qemu_setsockopt(slisten, IPPROTO_IPV6, IPV6_V6ONLY, &off,
                             sizeof(off));
         }