Update S3 test URL format from s3n:// to s3a://

[zz22394]

About S3 test cases, should I change the s3n:// test cases into s3a://?

eg.
https://github.com/Teradata/presto/blob/master/presto-hive/src/test/java/com/facebook/presto/hive/TestPrestoS3FileSystem.java#L71

It is still using s3n:// protocol, however now recommended S3 Client for Hadoop 2.7 and later is s3a://.
Please reference here:
http://wiki.apache.org/hadoop/AmazonS3

[petroav]

@zz22394 This community PR is related prestodb#5940, although it doesn't address tests.