Drop webserver rendering logging to VLOG(3)

Change-Id: Ic6e8b9b2dc98adca1982914a1714f82d13907ff7
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4196
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: Henry Robinson <henry@cloudera.com>
Improved benchmark report formatting

- Results are displayed more compactly in the report
- Only nodes with significant performance changes are displayed in execution summary comparisons

Change-Id: I51fe1f71760ba451b23d3d0ec31358c848e54976
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3979
Reviewed-by: Taras Bobrovytsky <tbobrovytsky@cloudera.com>
Tested-by: jenkins