Deadlock when issuing for multiple names

[jsha]

I pushed some trivial changes to the Certbot acme-v2 branch, fixing field names, which should have fixed the tests. And indeed, locally a run of:

python ./tools/chisel2.py le.wtf

Works (with le.wtf aliased to localhost in /etc/hosts). But in Travis, a request for /my-order/xyz times out. A little poking suggests that this is because Travis attempts issuance for multiple names at once, and there is a deadlock related to locking the order object.