CBLT-159:  do "s3mcd ls" after "s3cmd put" to check for success

Change-Id: Ia5e3c6483836912afe549bf55c36a932bd28fdaa
Reviewed-on: http://review.couchbase.org/38019
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>