frameworks/av: fix for testAACEncoder CTS testcase

- testAACEncoders CTS testcase is failing for
  Hardware aac encoder use case

- hardware encoder has bitrate limitation
  due to which  CTS testcase is failing

- Removed hardware AAC encoder component from MediaCodec list,
  added in OMXCodec path on specific request from
  Stagefright recorder

Change-Id: Idff8abf4b768f63262da0576768fb13c9d6df1de