lds/cds docs: clarify that static listeners/clusters cannot be modified (#381)

Signed-off-by: Matt Klein <mklein@lyft.com>

docs/root/api-v1/cluster_manager/cds.rst

@@ -42,6 +42,4 @@ JSON schema:
 clusters
   *(Required, array)* A list of :ref:`clusters <config_cluster_manager_cluster>` that will be
   dynamically added/modified within the cluster manager. Envoy will reconcile this list with the
-  clusters that are currently loaded and either add/modify/remove clusters as necessary. Note that
-  any clusters that are statically defined within the Envoy configuration cannot be modified via
-  the CDS API.
+  clusters that are currently loaded and either add/modify/remove clusters as necessary.

docs/root/configuration/cluster_manager/cds.rst

@@ -7,6 +7,11 @@ The cluster discovery service (CDS) is an optional API that Envoy will call to d
 cluster manager members. Envoy will reconcile the API response and add, modify, or remove known
 clusters depending on what is required.
 
+.. note::
+
+  Any clusters that are statically defined within the Envoy configuration cannot be modified or
+  removed via the CDS API.
+
 * :ref:`v1 CDS API <config_cluster_manager_cds_v1>`
 * :ref:`v2 CDS API <v2_grpc_streaming_endpoints>`
 

docs/root/configuration/listeners/lds.rst

@@ -23,6 +23,11 @@ The semantics of listener updates are as follows:
   be gracefully closed (if possible) for some period of time before the listener is removed and any
   remaining connections are closed. The drain time is set via the :option:`--drain-time-s` option.
 
+  .. note::
+
+    Any listeners that are statically defined within the Envoy configuration cannot be modified or
+    removed via the LDS API.
+
 Configuration
 -------------