[autotest] audio_facade: Add get_plugged_node_types method

Add get_plugged_node_types method to query plugged node types on Cros
device.

BUG=chromium:532713
TEST=not used yet

Change-Id: Ie0888fce81614c4217e0278257e59610da7d810a
Reviewed-on: https://chromium-review.googlesource.com/301342
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@chromium.org>
2 files changed