Support legacy E-AC-3 scheme id uri in dash manifests

[hbofolts1]

[REQUIRED] Use case description

I am attempting to parse dash manifests that have a schemeIdUri attribute value of urn:dolby:dash:audio_channel_configuration:2011 within the AudioChannelConfiguration element. The DashManifestParser implementation does not look for this value.

https://github.com/google/ExoPlayer/blob/release-v2/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java#L1086

       <AudioChannelConfiguration
         schemeIdUri="urn:dolby:dash:audio_channel_configuration:2011"
         value="F801">

Proposed solution

Similar to what shaka player is doing, the urn:dolby:dash:audio_channel_configuration:2011 string should also lead to calling parseDolbyChannelConfiguration.

https://github.com/google/shaka-player/blob/master/lib/dash/dash_parser.js#L1268