Fix various minor issues found by LGTM

- Unnecessary boxing
- Integer overflow
- Path traversal via zip
- Dangerous synchronization pattern

airsonic-main/src/main/java/org/airsonic/player/controller/PodcastReceiverAdminController.java

@@ -84,7 +84,7 @@ public class PodcastReceiverAdminController {
     }
 
     private void download(int[] episodeIds) {
-        for (Integer episodeId : episodeIds) {
+        for (int episodeId : episodeIds) {
             PodcastEpisode episode = podcastService.getEpisode(episodeId, false);
             if (episode != null && episode.getUrl() != null &&
                 (episode.getStatus() == PodcastStatus.NEW ||

airsonic-main/src/main/java/org/airsonic/player/controller/StreamController.java

@@ -311,7 +311,7 @@ public class StreamController  {
             return file.getFileSize();
         }
 
-        return duration * maxBitRate * 1000L / 8L;
+        return duration * (long)maxBitRate * 1000L / 8L;
     }
 
     private HttpRange getRange(HttpServletRequest request, MediaFile file) {

airsonic-main/src/main/java/org/airsonic/player/controller/UploadController.java

@@ -173,6 +173,9 @@ public class UploadController {
             while (entries.hasMoreElements()) {
                 ZipEntry entry = (ZipEntry) entries.nextElement();
                 File entryFile = new File(file.getParentFile(), entry.getName());
+                if (!entryFile.toPath().normalize().startsWith(file.getParentFile().toPath())) {
+                  throw new Exception("Bad zip filename: " + StringUtil.toHtml(entryFile.getPath()));
+                }
 
                 if (!entry.isDirectory()) {
 
@@ -263,4 +266,4 @@ public class UploadController {
         }
     }
 
-}
+}

airsonic-main/src/main/java/org/airsonic/player/monitor/MetricsManager.java

@@ -20,7 +20,7 @@ public class MetricsManager {
     // Main metrics registry
     private static final MetricRegistry metrics = new MetricRegistry();
 
-    private static Boolean metricsActivatedByConfiguration = null;
+    private static volatile Boolean metricsActivatedByConfiguration = null;
     private static Object _lock = new Object();
 
     // Potential metrics reporters