passt: Truncate PID file on open()

Otherwise, if the current PID has fewer digits than a previously
written one, the content will be wrong.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

passt.c

@@ -390,7 +390,7 @@ int main(int argc, char **argv)
 
 	if (*c.pid_file) {
 		if ((pidfile_fd = open(c.pid_file,
-				       O_CREAT | O_WRONLY | O_CLOEXEC,
+				       O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
 				       S_IRUSR | S_IWUSR)) < 0) {
 			perror("PID file open");
 			exit(EXIT_FAILURE);