HDFS-14321. Fix -Xcheck:jni issues in libhdfs, run ctest with -Xcheck:jni enabled. Contributed by Sahil Takiar.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>

hadoop-hdfs-project/hadoop-hdfs-native-client/pom.xml

@@ -243,6 +243,7 @@ http://maven.apache.org/xsd/maven-4.0.0.xsd">
                     <exec executable="ctest" failonerror="true" dir="${project.build.directory}/">
                       <arg line="--output-on-failure"/>
                       <arg line="${native_ctest_args}"/>
+                      <env key="LIBHDFS_OPTS" value="${env.LIBHDFS_OPTS} -Xcheck:jni"/>
                       <env key="CLASSPATH" value="${test_classpath}:${compile_classpath}"/>
                       <!-- Make sure libhadoop.so is on LD_LIBRARY_PATH. -->
                       <env key="LD_LIBRARY_PATH" value="${env.LD_LIBRARY_PATH}:${project.build.directory}/native/target/usr/local/lib:${hadoop.common.build.dir}/native/target/usr/local/lib"/>

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/hdfs.c

@@ -2508,7 +2508,7 @@ int hadoopRzOptionsSetByteBufferPool(
         // Delete any previous ByteBufferPool we had.
         (*env)->DeleteGlobalRef(env, opts->byteBufferPool);
     }
-    opts->byteBufferPool = byteBufferPool;
+    opts->byteBufferPool = (*env)->NewGlobalRef(env, byteBufferPool);
     return 0;
 }