Revert "WMF: fixed MediaPlayer buffering logic."

This reverts commit d599f7319af86265083bae96f21d942aeff24737.

This was not the correct logic...
According to the documentation, the BufferedMedia status should be
set only when in the PlayingState.

Change-Id: I36053ebc09c0517fcd2a1a7f2b091fbe8f04f3d0
Reviewed-by: Christian Stromme <christian.stromme@digia.com>
WMF: fixed various media player issues.

- Switch to BufferedMedia only once playback actually started, not when
requesting to start.
- Report the position to have changed when seeking in stopped state.

Change-Id: I930b3e6977cebe5935ed033d0a4d4e1eb899ad2c
Reviewed-by: Christian Stromme <christian.stromme@digia.com>