do not merge - Fix for issue 2184627 cherry picked from eclair-mr2

Bluetooth A2DP suspend-resume improvements.

This change will reduce the occurence rate of A2DP sink suspend resume failures observed in issues 2184627, 2181005 and possibly 2189628.

More robust suspend/resume logic.
Use only the suspend request to audio hardware to avoid having two concurent suspend resume control paths.