The POST endpoint for /api/providers doesn't support PhysicalInfraManager providers

[vwbusguy]

We have a situation where we have dozens of iLO instances that we want to add to ManageIQ via RedFish and doing this one at a time through the web interface has been tedious, so we attempted to add them through the REST API (per https://www.manageiq.org/docs/reference/euwe/doc-REST_API/miq/index#create-provider ).

Unfortunately, making an authenticated POST call to /api/providers to add a redfish provider results in the error:
"Unsupported request class ManageIQ::Providers::Redfish::PhysicalInfraManager"

This type show up with making an OPTIONS call to the /api/providers endpoint and redfish providers of this type show with GET calls.

For context, I first asked about this on gitter and @agrare responded:

it is failing here https://github.com/ManageIQ/manageiq-api/blob/master/app/controllers/api/providers_controller.rb#L142
looks like there isn't a create_action identifier for physical_infra_managers

[vwbusguy]

Thanks! I pulled the change here and verified that the API calls are now working to provision redfish instances.