simplify code and use members directly

core/src/main/java/org/elasticsearch/index/translog/Translog.java

@@ -542,6 +542,7 @@ public class Translog extends AbstractIndexShardComponent implements IndexShardC
     public boolean ensureSynced(Location location) throws IOException {
         try (ReleasableLock lock = readLock.acquire()) {
             if (location.generation == current.generation) { // if we have a new one it's already synced
+                ensureOpen();
                 return current.syncUpTo(location.translogLocation + location.size);
             }
         }

core/src/main/java/org/elasticsearch/index/translog/TranslogWriter.java

@@ -173,10 +173,8 @@ public class TranslogWriter extends TranslogReader {
         if (syncNeeded()) {
             try (ReleasableLock lock = writeLock.acquire()) {
                 ensureOpen();
-                final long offset = writtenOffset;
-                final int opsCount = operationCounter;
-                checkpoint(offset, opsCount, channelReference);
-                lastSyncedOffset = offset;
+                checkpoint(writtenOffset, operationCounter, channelReference);
+                lastSyncedOffset = writtenOffset;
             }
         }
     }