[#69457338] Clean up http_handler_test

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
[#69457338] Make trafficcontroller.HttpHandler a http.Handler

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>
[#69457338] Use HttpHandler for /recent

Signed-off-by: Alex Jackson <ajackson@pivotallabs.com>