Add missed discoverable policy rules for flavor-manage v3

Add discoverable policy rule for v3 extension flavor-manage,
Although without this patch, it also works. But that's used to
indicate to user there is option for flavor-manager discoverable.

Change-Id: I23f8bbaccfa104a12e4a4c9eea8bf04107b57d43
Add instanceset info to StartInstance response

Currently startinstance response doesn't have the
instanceset information with InstanceID, current state
and previous state. It just returns the "True".
As per the AWS API reference document, the StartInstance
response elements should include the instanceset information
as below:
<StartInstancesResponse xmlns="http://ec2.amazonaws.com/doc/2014-02-01/">
  <requestId>req-a7326465-5ce2-4ed6-ab89-394b38cca85f</requestId>
  <instancesSet>
    <item>
      <instanceId>i-00000001</instanceId>
      <currentState>
        <code>16</code>
        <name>running</name>
      </currentState>
      <previousState>
        <code>80</code>
        <name>stopped</name>
      </previousState>
    </item>
  </instancesSet>
</StartInstancesResponse>

Included the instanceset in to startinstance response elements
and updated the test cases for startinstance response elements
in nova/tests/api/ec2/test_cloud.py file.

Change-Id: I08ef7ed88f983b66a30c76d6b7b754222097a03b
Closes-bug: #1321220
Merge "Add instanceset info to StartInstance response"
Merge "Add missed discoverable policy rules for flavor-manage v3"