Fix how our load-tests pick a random language and app.
Fix how our load-tests pick a random language and app.

This makes sure we actually hit the legacy pages no matter
how many clients are configured during a locust run.

mozilla/addons-server,wagnerand/addons-server,mozilla/addons-server,mozilla/olympia,aviarypl/mozilla-l10n-addons-server,wagnerand/addons-server,eviljeff/olympia,diox/olympia,atiqueahmedziad/addons-server,psiinon/addons-server,diox/olympia,kumar303/addons-server,lavish205/olympia,lavish205/olympia,wagnerand/addons-server,kumar303/olympia,kumar303/olympia,aviarypl/mozilla-l10n-addons-server,aviarypl/mozilla-l10n-addons-server,diox/olympia,psiinon/addons-server,bqbn/addons-server,aviarypl/mozilla-l10n-addons-server,mozilla/olympia,bqbn/addons-server,mozilla/addons-server,psiinon/addons-server,atiqueahmedziad/addons-server,kumar303/olympia,wagnerand/olympia,lavish205/olympia,eviljeff/olympia,kumar303/olympia,psiinon/addons-server,wagnerand/olympia,mozilla/olympia,diox/olympia,eviljeff/olympia,bqbn/addons-server,kumar303/addons-server,atiqueahmedziad/addons-server,wagnerand/olympia,wagnerand/olympia,eviljeff/olympia,kumar303/addons-server,mozilla/addons-server,mozilla/olympia,atiqueahmedziad/addons-server,lavish205/olympia,kumar303/addons-server,wagnerand/addons-server,bqbn/addons-server