Update default deployment namespace to be 'cert-manager'

[munnerz]

What this PR does / why we need it:

Previously, our deployment manifests deployed into the 'default' namespace. This changes them to deploy into 'cert-manager' instead.

Release note:

The static deployment manifests now automatically deploy into the 'cert-manager' namespace by default

[munnerz]

/retest

[munnerz]

/retest

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

Approval requirements bypassed by manually added approval.

This pull-request has been approved by:

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these OWNERS Files:

• OWNERS

You can indicate your approval by writing /approve in a comment
You can cancel your approval by writing /approve cancel in a comment

[munnerz]

/hold

[munnerz]

Holding this until we've updated it to also make changing leader election namespace and cluster resource namespace easy too.

[wallrj]

Looks good, but one question.

The docs suggest installing cert manager in kube-system:

• https://github.com/jetstack/cert-manager/blob/master/docs/user-guides/deploying.md

Why not make that the default?

[munnerz]

@wallrj #329 is also switching the default cluster namespace be that of the cert-manager pod. I was generally trying to move towards cert-manager self contained in a single namespace (including the leader election configmap too).

I've held this PR, in order to update the docs & other places to do this, as merging now would cause a mixture of kube-system and the pods namespace to be used by default which is a bit messy.

[davecheney]

LGTM. Thanks

[jetstack-ci-bot]

/test all [submit-queue is verifying that this PR is safe to merge]

[jetstack-ci-bot]

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions here.