wrap fork so we can drop priority in child processes

src/mod/formats/mod_shell_stream/mod_shell_stream.c

@@ -108,7 +108,7 @@ static switch_status_t shell_stream_file_open(switch_file_handle_t *handle, cons
 	if (pipe(context->fds)) {
 		goto error;
 	} else {					/* good to go */
-		context->pid = fork();
+		context->pid = switch_fork();
 
 		if (context->pid < 0) {	/* ok maybe not */
 			goto error;