Change Thread.join on exit to a timed Thread.join

"Thread-11" prio=10 tid=0x00007fcd00a9b400 nid=0x751d waiting on condition [0x0000000042458000..0x0000000042458d00]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
        at java.lang.Thread.sleep(Native Method)
        at org.apache.hadoop.ipc.Client.stop(Client.java:667)
        at org.apache.hadoop.ipc.RPC$ClientCache.stopClient(RPC.java:189)
        at org.apache.hadoop.ipc.RPC$ClientCache.access$400(RPC.java:138)
        at org.apache.hadoop.ipc.RPC$Invoker.close(RPC.java:229)
        - locked <0x00007fcd06c6b470> (a org.apache.hadoop.ipc.RPC$Invoker)
        at org.apache.hadoop.ipc.RPC$Invoker.access$500(RPC.java:196)
        at org.apache.hadoop.ipc.RPC.stopProxy(RPC.java:353)
        at org.apache.hadoop.hdfs.DFSClient.close(DFSClient.java:213)
        - locked <0x00007fcd06c6b3a0> (a org.apache.hadoop.hdfs.DFSClient)
        at org.apache.hadoop.hdfs.DistributedFileSystem.close(DistributedFileSystem.java:243)
        at org.apache.hadoop.fs.FileSystem$Cache.closeAll(FileSystem.java:1413)
        - locked <0x00007fcd06ab9b68> (a org.apache.hadoop.fs.FileSystem$Cache)
        at org.apache.hadoop.fs.FileSystem.closeAll(FileSystem.java:236)
        at org.apache.hadoop.fs.FileSystem$ClientFinalizer.run(FileSystem.java:221)
        - locked <0x00007fcd06aaeee0> (a org.apache.hadoop.fs.FileSystem$ClientFinalizer)

    // wait until all connections are closed
    while (!connections.isEmpty()) {
      try {
        Thread.sleep(100);
      } catch (InterruptedException e) {
      }
    }