Add logic to fall back to simulation mode in the absence of the CAN interface,
based on a modified form of the dropped changes from patch #2 of:
https://gerrit.automotivelinux.org/gerrit/#/c/7641
This should fix SPEC-383 by allowing the HVAC demo to run on setups without
the CAN hardware again.
Bug-AGL: SPEC-383
Change-Id: I3ee11c92baccde427986ceb077a37e9b9c900b11
Signed-off-by: Scott Murray <scott.murray@konsulko.com>