Fix keda templates & namespace config

[liliankasem]

Issue describing the changes in this PR

resolves #1883

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• I have added all required tests (Unit tests, E2E tests)

Additional information

When running func kubernetes install --namespace myns for V2, the namespace value is ignored the templates do not have KEDA_NAMESPACE string to replace. I've updated the V2 templates to replace the default namespaces with KEDA_NAMESPACE so that we do actually take the namespace into account. Instead we now programmatically set the default value is the namespace is not provided.

I also found that when a namespace is not provided, we still return "true" on CreateNamespace without actually checking if a default namespace exists. This results in the action failing if we do not provide a namespace and the "default" namespace does not exist. Fixed this by checking for the config namespace, and if not set, we provide a default namespace value instead of leaving namespace as null.