zebra: Don't bind netns ID netlink socket to mcast groups

The netlink socket in `zebra_ns_id_get()` is only used to get netns id.
There's no need to subscribe to multicast groups. In some heavy-loaded
cases, unexpected notification races with normal reply message and
causes failure:

    zebra[110338]: [NMNEE-JJKPF][EC 4043309094] netlink recvmsg: bad sequence number 505ac8 (expected 66ea845f)

BTW, to subscribe to RTNLGRP_NSID, `nl_groups` should be
`1 << (RTNLGRP_NSID - 1)`. This code has never worked as expected.

Signed-off-by: Xiao Liang <[email protected]>

zebra/zebra_netns_id.c

@@ -180,7 +180,6 @@ ns_id_t zebra_ns_id_get(const char *netnspath, int fd_param)
 	}
 	memset(&snl, 0, sizeof(snl));
 	snl.nl_family = AF_NETLINK;
-	snl.nl_groups = RTNLGRP_NSID;
 	snl.nl_pid = 0; /* AUTO PID */
 	ret = bind(sock, (struct sockaddr *)&snl, sizeof(snl));
 	if (ret < 0) {