Different fixes for the S3 input and output plugins

- Input: Renaming the region config variable into region_endpoint to be inline with the output
- Input/Output: Making sure the endpoint urls are correct for all regions. ( based on PR #632 & #634 )
- Input/Output: added some extra logging info
Merge pull request #645 from electrical/s3_fixes

Different fixes for the S3 input and output plugins