control: Update zone target on startup

To handle restarting of the fan control service, set the zone's target
to what's initialized on one of the fan's target that's included in the
zone.

Change-Id: I88c598e817c1dbbd42d82265b8378dc78d3946d2
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/json/fan.cpp b/control/json/fan.cpp
index 9fbd03c..edd8514 100644
--- a/control/json/fan.cpp
+++ b/control/json/fan.cpp
@@ -89,6 +89,11 @@
 
 void Fan::setTarget(uint64_t target)
 {
+    if (_target == target)
+    {
+        return;
+    }
+
     for (const auto& sensor : _sensors)
     {
         auto value = target;