man: must set nodeid for knet in nodelist

Signed-off-by: Bin Liu <bliu@suse.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>

man/corosync.conf.5

@@ -650,7 +650,7 @@ nodeid
 This configuration option is required for each node. It is a 32 bit value 
 specifying the node identifier delivered to the
 cluster membership service. The node identifier value of zero is
-reserved and should not be used.
+reserved and should not be used. If knet is set, this field must be set.
 
 .PP
 Within the