Transcoder: Pass transcoding request parcel by value.

Fixes a HWASAN crash in CtsMediaTranscodingTestCases where
TranscoderWrapper reads the incoming request parcel asynchronously
without taking ownership of the memory.

Fixes: 183222648
Test: atest CtsMediaTranscodingTestCases:MediaTranscodeManagerTest
Change-Id: I27a667c1dfa46572f35a13af08fa9722eafaedbb
2 files changed