Istio Operator pauses reconciliation when gateway deployed to non-control plane namespace

Currently, gateways in member namespaces can only be reconciled after the SMCP has been fully reconciled (because that'll add the namespaces to the mesh) - so a possible workaround is to add the gateway only after a first complete reconciliation of the mesh. An implementation would likely have to parallelize namespace and SMCP reconciliation.

Deploying the following example should work (it's currently rejected by the operator):

apiVersion: maistra.io/v2
kind: ServiceMeshControlPlane
metadata:
  name: ossm-1718
spec:
  version: v2.2
  gateways:
    additionalIngress:
      istio-ingress-external:
        enabled: true
        namespace: bookinfo
---
apiVersion: maistra.io/v1
kind: ServiceMeshMemberRoll
metadata:
 name: default
spec:
 members:
 - bookinfo

Acceptance Criteria:

• operator should reconcile namespaces even if an SMCP isn't fully reconciled yet
• creating SMMR and SMCP (with gateway in non-control plane namespace) at the same time is possible

Original description:

Istio operator pauses all reconciliation when a gateway is deployed to namespace other than the control plane namespace.
This means that other operations, like adding a new namespace to the mesh cannot process.

Example SMCP: https://github.com/trevorbox/service-mesh-patterns/blob/ossm-2.0/ossm-2.0/helm/mongodb-trusted-ca/helm/control-plane/templates/servicemeshcontrolplane-basic-install.yaml

Errors observed in SMCP:

...
status:
  observedGeneration: 6
  annotations:
    alwaysReadyComponents: 'mesh-config,telemetry-common,tracing'
    readyComponentCount: 7/9
  readiness:
    components:
      pending:
        - istio-egress
        - kiali
      ready:
        - grafana
        - istio-discovery
        - istio-ingress
        - mesh-config
        - prometheus
        - telemetry-common
        - tracing
      unready: []
  operatorVersito update if on: 2.0.0-13.el8
...
  conditions:
    - lastTransitionTime: '2020-11-11T20:33:32Z'
      message: Successfully installed all mesh components
      reason: InstallSuccessful
      status: 'True'
      type: Installed
    - lastTransto update if itionTime: '2020-11-11T20:51:28Z'
      message: 'Paused until the following components become ready: [istio-egress]'
      reason: PausingUpdate
      status: 'False'
      type: Reconciled
    - lastTransitionTime: '2020-11-11T20:45:22Z'
      message: 'Paused until the following components become ready: [istio-egress]'
      reason: PausingUpdate
      status: 'False'
      type: Ready
...

Errors observed in istio-operator log:

...
{"level":"info","ts":1605127526.494948,"logger":"servicemeshmemberroll-controller","msg":"skipping reconciliation because mesh is not in a known good state","ServiceMeshMemberRoll":"istio-system/default"}
...