monitor: Shut down if no readings at power on

If there are no tach sensors on D-Bus when the power state changes to
on, then create an event log and shut down the system. This is done

monitor: Shut down if no readings at power on

If there are no tach sensors on D-Bus when the power state changes to
on, then create an event log and shut down the system. This is done
because in this case the code is not able to know the fan state - if
there are any present or spinning.

The most likely reason there are no sensors (aside from a glaring error
in the config file) is because the fan controller device driver failed
its probe and was unable to detect it, maybe because the device didn't
have power or there was an I2C problem. To aid in root cause analysis
if this were to occur in the field, the code adds the following FFDC
(First Failure Data Capture) to the event log:

* All of the loaded hwmon drivers, taken from /sys/class/hwmon/*/name
* Failure related lines in dmesg, which is where driver errors would
show up.

Tested: Unbound the fan device driver and then powered on the system.
Also disabled I2C to the fan controller device in simulation and tried a
power on.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Ic0b80d67ec79c9401f59324fe1134ff12084112a

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