Commit `ea085e72` added logic to reconcile the Ingress namespace during
cluster upgrades. This follow-up commit fixes some mistakes introduced
by that commit.

pkg/operator/controller/ingress/namespace.go:

Fix a typo: `opensift.io/cluster-monitoring`.
We are, after all, in the computing business, and not the baking
business.

Check if annotation/label map values exist since comparing a
non-existent map value to the empty string will always return true
in this case.

pkg/operator/controller/ingress/namespace_test.go:

Add unit test to prove that a map value that does not exist
is equivalent to the empty string.

Rename the `original` namespace to `desired`.
Switch ordering of `desired` and `mutated` in `routerNamespaceChanged`
calling sites to better reflect the intent of the unit tests.