Spark-1002 remove jars

So I had a doubt about the tests in FileServerSuite and have changed them. Having *uncommons* jar in the repo might be necessary. Even if a jar is created programmatically, how will it have a class that is not already on classpath ? and those tests try to load the class. 

So as an alternative it creates a jar with a file inside it and tests if that file is present on classpath after add jar is done.

Unfortunately, jenkins will not be able to test this PR.