stagefright: Adjust confidence threshold for extended sniffers

 * Some sniffers return 0.2 for cases where they only find an audio
   track in some containers.
 * Change the comparison to also examine files right on this threshold.
 * This allows us to score ONE FUCKING HUNDRED PERCENT on the Antutu
   Video Test \o/

Change-Id: I78b6ab8a634771e0e290f669801f5b08d6a32a51