fix(tests): silence obnoxious "possible memory leak detected" warning
fix(tests): silence obnoxious "possible memory leak detected" warning

https://github.com/mozilla/fxa-auth-server/pull/2110
r=shane-tomlinson
eoger/fxa-auth-server,mozilla/fxa-auth-server,eoger/fxa-auth-server,mozilla/fxa-auth-server,mozilla/fxa-auth-server,eoger/fxa-auth-server,eoger/fxa-auth-server,mozilla/fxa-auth-server