Set tach sensor inventory functional state

At startup, initialize the functional state of each tach sensor to true
and then update the inventory's functional state to match the tach
sensor's functional state.

Resolves openbmc/openbmc#2629

Change-Id: If608e4c044d9eeaa3dbdafa22bc89327e323c9a8
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/monitor/tach_sensor.hpp b/monitor/tach_sensor.hpp
index 59b99d2..ba3465a 100644
--- a/monitor/tach_sensor.hpp
+++ b/monitor/tach_sensor.hpp
@@ -94,12 +94,9 @@
         }
 
         /**
-         * Sets functional status
+         * Set the functional status and update inventory to match
          */
-        inline void setFunctional(bool functional)
-        {
-            _functional = functional;
-        }
+        void setFunctional(bool functional);
 
         /**
          * @brief Says if the timer is running or not
@@ -202,7 +199,7 @@
          * @brief If functional (not too slow).  The parent
          *        fan object sets this.
          */
-        bool _functional = true;
+        bool _functional;
 
         /**
          * @brief If the sensor has a Target property (can set speed)