sensorhandler: use entity-map from json if filled

Step 4 of the transition from YAML to JSON will return the data from the
JSON file if present and valid, otherwise it'll fallback and return the
default example YAML present in the repository.

Tested: This was not tested.
Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I33c773fc53660a9eb5e27a8c8c3e231c64fe079d
3 files changed