Modify api-ref information

Add response instruction for methods with no content returned.

Change-Id: I7261a0b30f2d27bf29ca953a37e0ef4a9857f127

api-ref/source/v1/instance_networks.inc

@@ -67,6 +67,11 @@ Request
 
 .. literalinclude:: samples/instance_networks/instance-associate-fip-req.json
 
+Response
+--------
+
+If successful, this method does not return content in the response body.
+
 
 Remove (Disassociate) Floating IP
 =================================
@@ -87,3 +92,8 @@ Request
 
     - instance_uuid: instance_ident
     - fip_address: address_path
+
+Response
+--------
+
+If successful, this method does not return content in the response body.

api-ref/source/v1/instance_states.inc

@@ -66,6 +66,11 @@ Request
 
 .. literalinclude:: samples/instance_states/instance-set-power-off.json
 
+Response
+--------
+
+If successful, this method does not return content in the response body.
+
 
 Change Instance Lock State
 ===========================
@@ -97,6 +102,11 @@ Request
 
 .. literalinclude:: samples/instance_states/unlock-instance.json
 
+Response
+--------
+
+If successful, this method does not return content in the response body.
+
 
 Change Instance Provision State
 ===============================
@@ -123,3 +133,8 @@ Request
 **Example request to rebuild an Instance:**
 
 .. literalinclude:: samples/instance_states/rebuild-instance.json
+
+Response
+--------
+
+If successful, this method does not return content in the response body.