Update iallocator design to include MonD data

Add "MonD data" sub-section.
Signed-off-by: Spyros Trigazis <strigazi@gmail.com>
Signed-off-by: Michele Tartara <mtartara@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>

doc/design-monitoring-agent.rst

@@ -49,6 +49,8 @@ The monitoring agent system will report on the following basic information:
 - Node OS CPU load average report
 - Information from a plugin system
 
+.. _monitoring-agent-format-of-the-report:
+
 Format of the report
 --------------------
 

doc/iallocator.rst

@@ -325,6 +325,16 @@ As for ``node-evacuate``, it needs the following request arguments:
   instances
     a list of request dicts
 
+MonD data
++++++++++
+
+Additional information is available from mond. Mond's data collectors
+provide information that can help an allocator script make better
+decisions when allocating a new instance. Mond's information may also be
+accessible from a mock file mainly for testing purposes. The file will
+be in JSON format and will present an array of :ref:`report objects
+<monitoring-agent-format-of-the-report>`.
+
 Response message
 ~~~~~~~~~~~~~~~~