CRAS: apm_list - Enable aec_dump

Adds cras client API to trigger start/stop of aec dump.

BUG=chromium:710465
TEST=cras_test_client --capture_file /tmp/1 --effects aec;
Run 'cras_test_client --dump_a | grep -C 3 Input'  to
look up the id of the stream.
Then execute 'cras_test_client --aecdump /tmp/aecdump --duration 10
--stream_id <stream-id>' and make sure /tmp/aecdump contains
correct information.

Change-Id: Ibb2e8cfa2e60fb158c926396cdd55568d671be92
Reviewed-on: https://chromium-review.googlesource.com/490589
Commit-Ready: Hsinyu Chao <hychao@chromium.org>
Tested-by: Hsinyu Chao <hychao@chromium.org>
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
12 files changed