monitor: Use the number of failed tach sensors at startup

When marking a fan nonfunctional due to its tach sensors failing
to be read from dbus, a check against the configured number of
sensors that should result in the fan being marked as nonfunctional
should be checked.

Tested:
    Run phosphor-fan-monitor --monitor in witherspoon qemu,
    when the number of failed tach sensor is larger than the
    configured _numSensorFailsForNonFunc then mark the
    associated fan as nonfunctional.

Change-Id: I6ff97b9aae4279d6ce402d3aecda087d45dfa318
Signed-off-by: Jolie Ku <jolie_ku@wistron.com>
3 files changed