Audio V4: Add metadata update to legacy API

The metadata API was not present in the legacy HAL which lots of
developer still use.

Test: Check the method is correctly called on each track change
Bug: 38184704
Bug: 69623109
Change-Id: If56b4ee3739194e49808cf24d728c791b0588f9f
Signed-off-by: Kevin Rocard <krocard@google.com>