DRILL-8242: Fix output for HttpHelperFunctions (#2568)
* DRILL-8242: Fix output for HttpHelperFunctions
- add test to check the http_get function output
* DRILL-8242: Fix output for HttpHelperFunctions
* DRILL-8242: Fix old approach for other functions
* DRILL-8242: replace String with InputStream for SimpleHTTP requests
* Fix TestHttpPlugin#testSlowResponse. Sometimes DATA_READ ERROR: Read timed out can be returned
