/kind bug

What happened:

When attempting to provision a secret to a namespace that has a quota enabled, I run into the following error:

error presenting acme authorization for domain "apiserver.myco.io": error ensuring http01 challenge pod: pods "cm-apiserver-proxy-ecjpz" is forbidden: failed quota: myco-quota: must specify limits.cpu,limits.memory]

The HTTP validation pod fails to create because the resource limits are not set in the http.go issuer pkg/issuer/acme/http/http.go:326

What you expected to happen:

A certificate is provisioned successfully in a namespace with a quota enabled

How to reproduce it (as minimally and precisely as possible):

Attempt to use http validation in a namespace with quota enabled

Environment:
quay.io/jetstack/cert-manager-controller:v0.2.2
quay.io/jetstack/cert-manager-ingress-shim:v0.2.2