image_uplaoder: add retry to _layer_stream_registry
image_uplaoder: add retry to _layer_stream_registry

We have seen that uploading a layer can be problematic if the fetch is
dropped by network issues (like it happens in OpenStack Infra).

This patch adds a retry to the function that fetch the layer and retry
if an HTTP exception is raised.

Change-Id: Ia9716447a7d037aaf32c3b01ab511c08e6598e07
Closes-Bug: #1815576

openstack/tripleo-common,openstack/tripleo-common