Use setFunctional when tach sensor is constructed

Change-Id: I32e30dc8f659172026258ca533099404c90aebbc
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/monitor/tach_sensor.cpp b/monitor/tach_sensor.cpp
index 1069313..2aa1609 100644
--- a/monitor/tach_sensor.cpp
+++ b/monitor/tach_sensor.cpp
@@ -79,8 +79,7 @@
     _timer(events, [this, &fan](){ fan.timerExpired(*this); })
 {
     // Start from a known state of functional
-    _functional = true;
-    updateInventory(_functional);
+    setFunctional(true);
 
     // Load in starting Target and Input values
     try