Support OpenShift 4.x SNO on vSphere

Feature Overview (aka. Goal Summary)  

An elevator pitch (value statement) that describes the Feature in a clear, concise way.  Complete during New status.

Support OpenShift SNO on vSphere via IPI  and ACM installation. <your text here>

Goals (aka. expected user outcomes)

The observable functionality that the user now has as a result of receiving this feature. Include the anticipated primary user type/persona and which existing features, if any, will be expanded. Complete during New status.

Currently, SNO on vSphere is supported only with "platform=none", which requires  some  manual steps / workarounds to quickly setup a SNO cluster. The goal of this feature is a quick IPI based installation of SNO on vSphere is fully supported, also with ACM.

Requirements (aka. Acceptance Criteria):

• IPI with platform=vsphere is supported
• ACM can install SNO on vsphere without any scripting needs.
• regular vsphere platform integration, esp. vsphere in-tree CSI driver 
•  

Questions to Answer (Optional):

Can In place bootstrapping to avoid  bootstrap vm and reduce installation time work?

Out of Scope

n/a

Background

Provide any additional context is needed to frame the feature.  Initial completion during Refinement status.

Esp. in industrial edge computing scenarios, we see a lot of vmware deployments. For customers slowly transitioning to k8s workload, SNO is a good option. 

Customer Considerations

Provide any additional customer-specific considerations that must be made when designing and delivering the Feature.  Initial completion during Refinement status.

See linked RFE for customer demands. We have an "early adopter" customer willing to test-drive this early and collaborate on the engineering side.

Documentation Considerations

Provide information that needs to be considered and planned so that documentation will meet customer needs.  If the feature extends existing functionality, provide a link to its current documentation. Initial completion during Refinement status.

OpenShift docs on SNO installation need to be updated. We can add it the same way as we already have AWS, GCP etc. in the docs: https://docs.openshift.com/container-platform/4.14/installing/installing_sno/install-sno-installing-sno.html#install-sno-installing-sno-on-cloud-providers

Interoperability Considerations

Which other projects, including ROSA/OSD/ARO, and versions in our portfolio does this feature impact?  What interoperability test scenarios should be factored by the layered products?  Initial completion during Refinement status.

• IPI SNO on any on-premise Platform deployment with keepalived is known to be broken: https://issues.redhat.com/browse/OCPBUGS-6508 gives context on when this was first discovered
• This is caused by keepalived automatically enabling unicast, which is a problem for SNO deployments since you need at least 2
  nodes for VRRP peering via Unicast: https://github.com/openshift/machine-config-operator/pull/4021 
• This causes SNO Deployments to fail and we will need to use the RFE that was the trigger for this issue to bring this Fix back to life.
• Additionally, this affects not only vSphere but all SNO on-Prem installations so we need to think how we would want to roll this out to avoid untested supported scenarios. I suggest we think about enabling this first for vSphere and using our test lane efforts that we anyhow wanted to build in assisted-installer and payload testing to fill the gap of the untested scenario. ( see https://issues.redhat.com/browse/OCPEDGE-912)