Fix Stats Collector to not divide by zero (#10492)

* Set loadHistory value to zero when interval is zero to not throw arithmatic exception

* Change loadHistory value to -1 and fix maxsize bug

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Co-authored-by: Lucas Martins <[email protected]>

Author: lucas-a-martins

server/src/main/java/com/cloud/server/StatsCollector.java

@@ -718,10 +718,10 @@ protected void runInContext() {
                  getDynamicDataFromDB();
                  long interval = (Long) dbStats.get(uptime) - lastUptime;
                  long activity = (Long) dbStats.get(queries) - lastQueries;
-                 loadHistory.add(0, Double.valueOf(activity / interval));
+                 loadHistory.add(0, interval == 0 ? -1 : Double.valueOf(activity / interval));
                  int maxsize = DATABASE_SERVER_LOAD_HISTORY_RETENTION_NUMBER.value();
                  while (loadHistory.size() > maxsize) {
-                     loadHistory.remove(maxsize - 1);
+                     loadHistory.remove(maxsize);
                  }
              } catch (Throwable e) {
                  // pokemon catch to make sure the thread stays running