Fixed a bug in finding the streaming jar file

The find command to find the Hadoop streaming jar file gets mixed up when there are source files in Hadoop folders, eg. the following:

```
hadoop-2.6.0/share/hadoop/tools/lib/hadoop-streaming-2.6.0.jar
hadoop-2.6.0/share/hadoop/tools/sources/hadoop-streaming-2.6.0-sources.jar
hadoop-2.6.0/share/hadoop/tools/sources/hadoop-streaming-2.6.0-test-sources.jar
```