kdat/net: Init kerndat even if nsid aren't supported

We should continue even if kdat feature isn't supported:

[criu]# ./criu/criu dump -t `pidof pypy` --shell-job
Warn  (criu/kerndat.c:804): Can't load /run/criu.kdat
Warn  (criu/libnetlink.c:55): ERROR -95 reported by netlink
Error (criu/net.c:3042): Unable to create a veth pair: -95
Warn  (criu/net.c:3064): NSID isn't reported for network links

Cc: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>

criu/net.c

@@ -3055,7 +3055,7 @@ int kerndat_link_nsid()
 
 	if (status) {
 		pr_warn("NSID isn't reported for network links\n");
-		return -1;
+		return 0;
 	}
 
 	kdat.has_link_nsid = true;