test_vendor_lib: Read controller properties from file.

This upload lets the controller be configured via a JSON file that
specifies the controller attributes. A default configuration is not
currently provided but will be included in a future upload. Also fixes
a few mistakes in test_channel.py.

Bug: 21586676
Change-Id: I9d0e65a9664e179ddb97664a748c766f4f8a554e