Fix zero-padding bug in python loadtest client.
Fix zero-padding bug in python loadtest client.

shane-tomlinson/fxa-auth-server,jamonation/fxa-auth-server,chilts/fxa-auth-server,eoger/fxa-auth-server,jamonation/fxa-auth-server,TDA/fxa-auth-server,chilts/fxa-auth-server,eoger/fxa-auth-server,mozilla/fxa-auth-server,shane-tomlinson/fxa-auth-server,TDA/fxa-auth-server,dannycoates/picl-idp,jamonation/fxa-auth-server,jrgm/fxa-auth-server,dannycoates/picl-idp,dannycoates/picl-idp,shane-tomlinson/fxa-auth-server,eoger/fxa-auth-server,TDA/fxa-auth-server,chilts/fxa-auth-server,eoger/fxa-auth-server,shane-tomlinson/fxa-auth-server,mozilla/fxa-auth-server,dannycoates/picl-idp,mozilla/fxa-auth-server,jamonation/fxa-auth-server,jrgm/fxa-auth-server,jrgm/fxa-auth-server,chilts/fxa-auth-server,TDA/fxa-auth-server,mozilla/fxa-auth-server,jrgm/fxa-auth-server