centralize shift behavior into TimeTracker func

lib/servers.js

@@ -26,23 +26,13 @@ class ServerRegistration {
     const playerCount = resp ? resp.players.online : null
 
     // Store into in-memory ping data
-    this._pingHistory.push(playerCount)
-
-    // Trim pingHistory to avoid memory leaks
-    if (this._pingHistory.length > TimeTracker.getMaxServerGraphDataLength()) {
-      this._pingHistory.shift()
-    }
+    TimeTracker.pushAndShift(this._pingHistory, playerCount, TimeTracker.getMaxServerGraphDataLength())
 
     // Only notify the frontend to append to the historical graph
     // if both the graphing behavior is enabled and the backend agrees
     // that the ping is eligible for addition
     if (updateHistoryGraph) {
-      this.graphData.push(playerCount)
-
-      // Trim old graphPoints according to #getMaxGraphDataLength
-      if (this.graphData.length > TimeTracker.getMaxGraphDataLength()) {
-        this.graphData.shift()
-      }
+      TimeTracker.pushAndShift(this.graphData, playerCount, TimeTracker.getMaxGraphDataLength())
     }
 
     // Delegate out update payload generation