0.5C granularity is enough and reduce number of KVS updates

pool.js

@@ -226,7 +226,7 @@ function update_temp(temp) {
   }
   status.lock_update = true;
 
-  status.temp = Math.round(temp * 10) / 10;
+  status.temp = Math.round(temp * 2) / 2;
 
   if (status.temp > status.temp_today || status.temp_today === null) {
     status.temp_today = status.temp;