Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Set default cluster resource namespace to current pod namespace
**What this PR does / why we need it**:
Changes the default cluster resource namespace from kube-system to the current namespace of the cert-manager deployment.
**Which issue this PR fixes**: fixes#103
**Release note**:
```release-note
Supporting resources for ClusterIssuer's (e.g. signing CA certificates, or ACME account private keys) will now be stored in the same namespace as cert-manager, instead of kube-system in previous versions. Action required: you will need to ensure to properly manually migrate these referenced resources across into the deployment namespace of cert-manager, else cert-manager may not be able to find account private keys or signing CA certificates.
```
/cc @mikebryant
