stagefright-plugins: Allow multiple getParameter invocations

 * Previously we asserted that the component was not yet configured
   during getParameter, but SF in Lollipop may need to query the
   component multiple times.  Add support for this.

Change-Id: I5e1de8a57605e682a543614414d4e1efac43d03f
stagefright-plugins: Enable 24-bit output

 * Always enable it. Audioflinger has conversions for when the hardware
   can't support it.
 * Also fix a bunch of state management issues

Change-Id: I2106b34251bd0c9db0655dd97d3e92c7b635a982