Mention NO_MASQ_LOCAL opt in the docs

site/kubernetes/kube-addon.md

@@ -355,6 +355,9 @@ The list of variables you can set is:
   a larger size for better performance if your network supports jumbo
   frames - see [here](/site/tasks/manage/fastdp.md#mtu) for more
   details.
+* `NO_MASQ_LOCAL` - set to 1 to preserve the client source IP address when
+  accessing Service annotated with `service.spec.externalTrafficPolicy=Local`.
+  The feature works only with Weave IPAM (default).
 
 Example:
 ```