S3: Allow DDL statements to reference non-HDFS file-systems

This will allow you to create tables around data that already exists on
S3.  (Though INSERT and LOAD DATA don't support S3 yet). Also this will
make it easier to create some test tables that are not on HDFS.

Also, workaround HDFS-7031 (which is a "won't fix") where non-defaultFS
paths can be qualified with the wrong authority. This is needed for
Impala now that it can take non-HDFS paths as input.

Change-Id: Ie513d50b26dfe5a71be284ad31a8c8151d0e30d3
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5417
Reviewed-by: Daniel Hecht <dhecht@cloudera.com>
Tested-by: jenkins