Fix detection of outdated sensorcache entries

CollectAgent/sensorcache.cpp

@@ -51,13 +51,17 @@ uint64_t SensorCache::getSensor(SensorId sid) {
 	}
 
 	if (it->second.deltaT.size()) {
-		uint64_t ts = Messaging::calculateTimestamp() / 1000000;
+		uint64_t ts = Messaging::calculateTimestamp();
 		uint64_t avg = 0;
 		for (std::list<uint32_t>::iterator dt = it->second.deltaT.begin(); dt !=  it->second.deltaT.end(); dt++) {
 			avg+= *dt;
 		}
 		avg/= it->second.deltaT.size();
-		if ((ts - it->second.timestamp) > 5 * avg) {
+		/*
+		 * A SID is outdated if it's older than 5x the average sampling period.
+		 * The 1000000 accounts for the conversion ns->ms in deltaT.
+		 */
+		if ((ts - it->second.timestamp) > 5 * 1000000 * avg) {
 			throw std::out_of_range("Sid outdated");
 		}
 	}