kdat: Don't open /run/criu.kdat if doesn't exists

When CRIU is called for a first time and the /run/criu.kdat file does
not exists, the following warning is shown:
        Warn  (criu/kerndat.c:847): Can't load /run/criu.kdat

This patch is replacing this warning with a more appropriate debug message.
        File /run/criu.kdat does not exist
Signed-off-by: Radostin Stoyanov <rstoyanov1@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/kerndat.c

@@ -835,7 +835,10 @@ static int kerndat_try_load_cache(void)
 
 	fd = open(KERNDAT_CACHE_FILE, O_RDONLY);
 	if (fd < 0) {
-		pr_warn("Can't load %s\n", KERNDAT_CACHE_FILE);
+		if(ENOENT == errno)
+			pr_debug("File %s does not exist\n", KERNDAT_CACHE_FILE);
+		else
+			pr_warn("Can't load %s\n", KERNDAT_CACHE_FILE);
 		return 1;
 	}