libstagefright: Fix for media player error during WMV streaming

-Issue: Power suspend and resume during WMV streaming is
 resulting "Sorry cannot play" error.
-Rootcause: While resuming streaming video, the WMA decoder is
 paused to stop reading input data until a subsequent seek.
 But it is not started again after seek. Hence subsequent read()
 call fails and error is thrown.
-Fix: Check audio source state and resume it after seek.

Change-Id: If3d2dd45c5aba97cf79901d2ea05f5261e3eabd9
CRs-Fixed: 555961