ingress: Fix up openshift-ingress namespace reconciliation
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.