Several fixes in AudioDumpInterface:

- forward setMode() and getInputBufferSize() calls to underlying audio hardware interface.
- Allow capture of more than one output stream (previous implementation was only capturing
the first output opened, namely the hardware output).
- Allow capture of input streams: previous implementation was only simulating input streams
when more than one was open at a time by reading from a file on SD card). Now the default
behavior is to capture PCM data read from input stream if it was successfully opened or
simulate capture otherwise.

Change-Id: I7e2892b25e295fc3c19c7eb0f71bfaea5816b73a