passt, tap: Don't use -1 as uninitialised value for fd_tap_listen

This is a remnant from the time we kept access to the original
filesystem and we could reinitialise the listening AF_UNIX socket.

Since commit 0515adceaa ("passt, pasta: Namespace-based sandboxing,
defer seccomp policy application"), however, we can't re-bind the
listening socket once we're up and running.

Drop the -1 initalisation and the corresponding check.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

passt.c

@@ -211,7 +211,7 @@ int main(int argc, char **argv)
 
 	isolate_initial();
 
-	c.pasta_netns_fd = c.fd_tap = c.fd_tap_listen = -1;
+	c.pasta_netns_fd = c.fd_tap = -1;
 
 	sigemptyset(&sa.sa_mask);
 	sa.sa_flags = 0;

tap.c

@@ -1304,7 +1304,6 @@ void tap_sock_init(struct ctx *c)
 	}
 
 	if (c->mode == MODE_PASST) {
-		if (c->fd_tap_listen == -1)
 		tap_sock_unix_init(c);
 
 		/* In passt mode, we don't know the guest's MAC address until it