chardev: do not use short form boolean options in non-QemuOpts character device descriptions

Options such as "-gdb" or "-serial" accept a part-QemuOpts part-parsed-by-hand
character device description.  Do not use short form boolean options in the
QemuOpts part.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index b7863b8..06a37c0 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -452,7 +452,7 @@
                                qemu_chr_socket_protocol(s),
                                s->addr->u.inet.host,
                                s->addr->u.inet.port,
-                               s->is_listen ? ",server" : "");
+                               s->is_listen ? ",server=on" : "");
         break;
     case SOCKET_ADDRESS_TYPE_UNIX:
     {
@@ -470,12 +470,12 @@
 
         return g_strdup_printf("%sunix:%s%s%s%s", prefix, sa->path,
                                abstract, tight,
-                               s->is_listen ? ",server" : "");
+                               s->is_listen ? ",server=on" : "");
         break;
     }
     case SOCKET_ADDRESS_TYPE_FD:
         return g_strdup_printf("%sfd:%s%s", prefix, s->addr->u.fd.str,
-                               s->is_listen ? ",server" : "");
+                               s->is_listen ? ",server=on" : "");
         break;
     case SOCKET_ADDRESS_TYPE_VSOCK:
         return g_strdup_printf("%svsock:%s:%s", prefix,
@@ -607,7 +607,7 @@
     case AF_UNIX:
         return g_strdup_printf("unix:%s%s",
                                ((struct sockaddr_un *)(ss))->sun_path,
-                               s->is_listen ? ",server" : "");
+                               s->is_listen ? ",server=on" : "");
 #endif
     case AF_INET6:
         left  = "[";
@@ -621,7 +621,7 @@
         return g_strdup_printf("%s:%s%s%s:%s%s <-> %s%s%s:%s",
                                qemu_chr_socket_protocol(s),
                                left, shost, right, sserv,
-                               s->is_listen ? ",server" : "",
+                               s->is_listen ? ",server=on" : "",
                                left, phost, right, pserv);
 
     default: