Fix dcdbpusher not terminating if no thraeds executing sensor groups are available

dcdbpusher/includes/SensorGroupInterface.h

@@ -68,11 +68,22 @@ public:
 
 	/**
 	 * Does a busy wait until all dispatched handlers are finished (_pendingTasks == 0)
+	 * If the wait takes longer than a reasonable amount of time we return anyway,
+	 * to not block termination of dcdbpusher.
 	 */
 	void wait() {
-		while(_pendingTasks) {
-			sleep(1);
-		}
+	    unsigned short retries = 3;
+
+	    for (unsigned short i = 1; i <= retries; i++) {
+	        if (_pendingTasks) {
+	            LOG(info) << "Group " << _groupName << " not yet finished. Waiting... (" << i << "/" << retries << ")";
+	            sleep((_interval/1000) + 1);
+	        } else {
+	            return;
+	        }
+	    }
+
+	    LOG(warning) << "Group " << _groupName << " will not finish! Skipping it";
 	}
 
 	//can be overwritten