RocksJava] Fix ColumnFamily tests

Summary:
Cleaned up some tests regarding disposal order and tests
which were failing when C++ assertions were enabled.

Test Plan:
- Enable C++ Assertions (remove e.g. -DNDebug in rocksdbjava target)
- make rocksdbjava jtest

Reviewers: adamretter, ankgup87, yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D34569

java/benchmark/src/main/java/org/rocksdb/benchmark/DbBenchmark.java

@@ -418,9 +418,11 @@ public class DbBenchmark {
         stats_.found_++;
         stats_.finishedSingleOp(iter.key().length + iter.value().length);
         if (isFinished()) {
+          iter.dispose();
           return;
         }
       }
+      iter.dispose();
     }
   }
 

java/src/test/java/org/rocksdb/ColumnFamilyTest.java

@@ -723,7 +723,7 @@ public class ColumnFamilyTest {
     try {
       options = new Options().setCreateIfMissing(true);
       db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath());
-      final String simplifiedChinese = "简体字";
+      final String simplifiedChinese = "\u7b80\u4f53\u5b57";
       columnFamilyHandle = db.createColumnFamily(
           new ColumnFamilyDescriptor(simplifiedChinese.getBytes()));