One of the "fun" aspects of accessing OCI images, is we have no way
to realistically gain awareness of the underlying disk format in the
OCI model, at least unless it is hinted at in the data model.
Where we're unable to really figure that out is when a user
supplies a specific digest URL. Ironic recognizes this and "right sizes"
the process and data discovery and explicitly notes the disk format it
believe to be 'unknown'.
In order for IPA to be able to stream, and appropriately check
this data format, IPA has be "okay" with 'unknown'. Everything else
appears good to get to this point. This doesn't prohibit the image
safety checking, just allows for the perception mismatch when the
format is 'unknown'
Change-Id: Ibe38245e906c659057a3c5ea7d8a0e474599ff5c
c4998fc584