Associate BMC health sensors with chassis

This change adds association between the sensors and the bmc, such
that the BMC health sensors are ready to be picked up by bmcweb.

Tested: Added a BMC in phosphor-inventory, made a few temporary
changes to bmcweb so it treats BMCs as a chassis and populates
/redfish/v1/Chassis/bmc/Sensor entries, set up webui-vue, saw
the sensor readings in browser.

Change-Id: I1b5b9e9c97b37ecdef916712cb9f345858eb1ada
Signed-off-by: Sui Chen <suichen6@gmail.com>
2 files changed