more volume support

- add master volume only case:
  some H/W can have only single master volume.
  In that case, all volume change will be sent to stream 0.
  TODO: do better handling of master volule only case

- add no_auto_get in vns_policy.xml so that subscription does not
  lead into auto get for some properties

bug: 28175862

Change-Id: I0aa7a8a54385704620c28aaa0f21898bdc1e8164
7 files changed