qemu-ga: Plug fd leak on ga_channel_listen_accept() error path

Spotted by Coverity.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMichael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: NLuiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

qga/channel-posix.c

@@ -46,6 +46,7 @@ static gboolean ga_channel_listen_accept(GIOChannel *channel,
     ret = ga_channel_client_add(c, client_fd);
     if (ret) {
         g_warning("error setting up connection");
+        close(client_fd);
         goto out;
     }
     accepted = true;