[Minor] Store shuffleId int to be consistent with other data structure (

#10)

### What changes were proposed in this pull request?
Store shuffleId int to be consistent with other data structure

### Why are the changes needed?
Store shuffleId int to be consistent with other data structure, like the `partitionsToBlockIds` and `commitLocks`.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
No need.

server/src/main/java/com/tencent/rss/server/ShuffleTaskManager.java

@@ -76,7 +76,7 @@ public class ShuffleTaskManager {
   private ShuffleBufferManager shuffleBufferManager;
   private Map<String, Long> appIds = Maps.newConcurrentMap();
   // appId -> shuffleId -> commit count
-  private Map<String, Map<Long, AtomicInteger>> commitCounts = Maps.newConcurrentMap();
+  private Map<String, Map<Integer, AtomicInteger>> commitCounts = Maps.newConcurrentMap();
   private Map<String, Map<Integer, Object>> commitLocks = Maps.newConcurrentMap();
   // appId -> shuffleId -> blockIds
   private Map<String, Map<Integer, Roaring64NavigableMap>> cachedBlockIds = Maps.newConcurrentMap();
@@ -229,9 +229,9 @@ public void addFinishedBlockIds(
     }
   }
 
-  public int updateAndGetCommitCount(String appId, long shuffleId) {
+  public int updateAndGetCommitCount(String appId, int shuffleId) {
     commitCounts.putIfAbsent(appId, Maps.newConcurrentMap());
-    Map<Long, AtomicInteger> shuffleCommit = commitCounts.get(appId);
+    Map<Integer, AtomicInteger> shuffleCommit = commitCounts.get(appId);
     shuffleCommit.putIfAbsent(shuffleId, new AtomicInteger(0));
     AtomicInteger commitNum = shuffleCommit.get(shuffleId);
     return commitNum.incrementAndGet();