Notify users when platform is undergoing upgrade

Epic Goal*
As an OpenShift non-Admin user, who is not performing the OpenShift update, I want to be informed when the cluster is undergoing an update.

• Display a notification/banner throughout OCP web UI saying that the cluster is currently under upgrade.
• Generate a notification or alert for all the users to indicate cluster is undergoing an upgrade.

What is our purpose in implementing this?  What new capability will be available to customers?

Why is this important? (mandatory)

When cluster administrators perform an upgrade of the cluster, this can impact application teams using the cluster. For example, Maven pods can be evicted from the node being upgraded leading to a failed build, causing teams to waste time investigating why their build failed. Applications will be restarted unexpectedly when they are evicted from the node being upgraded, causing teams to waste time investigating why their application restarted. Applications may experience issues after the upgrade was finished because of incompatibility

Created from: https://issues.redhat.com/browse/RFE-3024

What are the benefits to the customer or Red Hat?   Does it improve security, performance, supportability, etc?  Why is work a priority?

This provides a better UX for all OpenShift users so they can set expectations of a potential degradation in OpenShift service during an update.

Scenarios (mandatory) 

Provide details for user scenarios including actions to be performed, platform specifications, and user personas.  

Dependencies (internal and external) (mandatory)

What items must be delivered by other teams/groups to enable delivery of this epic. 

Contributing Teams(and contacts) (mandatory) 

Our expectation is that teams would modify the list below to fit the epic. Some epics may not need all the default groups but what is included here should accurately reflect who will be involved in delivering the epic.

• Development - 
• Documentation -
• QE - 
• PX - 
• Others -

Acceptance Criteria (optional)

Provide some (testable) examples of how we will know if we have achieved the epic goal.  

Drawbacks or Risk (optional)

Reasons we should consider NOT doing this such as: limited audience for the feature, feature will be superseded by other work that is planned, resulting feature will introduce substantial administrative complexity or user confusion, etc.

Done - Checklist (mandatory)

The following points apply to all epics and are what the OpenShift team believes are the minimum set of criteria that epics should meet for us to consider them potentially shippable. We request that epic owners modify this list to reflect the work to be completed in order to produce something that is potentially shippable.

• CI Testing - Tests are merged and completing successfully
• Documentation - Content development is complete.
• QE - Test scenarios are written and executed successfully.
• Technical Enablement - Slides are complete (if requested by PLM)
• Other