AudioRecord: fix issues with privacy sensitive mode

Fix two issues with privacy sensitive mode implementation:
1) default applied by AudioAttributes based on source could
override explicit flag set.
2) when privacy mode was explicitly set in AudioRecord builder,
the audio source was reset.

Bug: 137850106
Test: CTS test for AudioRecord
Change-Id: I73f69d3d214102dcc237cac616c9bfc3f85b288e