Use http_logs for performance/regression testing

[Jon-AtAWS]

Is your feature request related to a problem? Please describe.

I noticed (#673) we seem to be using nyc_taxis for performance and regression testing. nyc_taxis is representative of some portion of user workloads and is worth testing. However, more users have semi-structured, mixed text and numeric data. The http_logs data set in ESRally is a much better representation of these workloads.

Describe the solution you'd like
Add testing for http_logs as part of performance/regression testing. Alternately, replace nyc_taxis entirely and use http_logs instead.