Made some minor adjustments

src/backing.c

@@ -447,6 +447,16 @@ result_t get_backing_info(disk_info_t* _info, const char* backing) {
 }
 
 result_t sync_backing_pool(void) {
+	// Check that the file /etc/sandbox.d/sync exists
+	struct stat st;
+	errno = 0;
+	if (stat("/etc/sandbox.d/sync", &st) != 0) {
+		if (errno == ENOENT)
+			return success();
+		else
+			return failure("Failed to check if /etc/sandbox.d/sync exists (%s).", strerror(errno));
+	}
+
 	// Execute /etc/sandbox.d/sync with the backing pool as the working directory
 	int exit_code;
 	// char* stdoutbuf;