This patch adds a first step towards image introspection. The patch adds
a set of tasks to correctly import an image from an external source (old
copy-from) and then introspect the image.
The implementation keeps these 2 implementations separate by considering
the import process a top-level task and the introspection step an
optionally available task that may/may not succeed.
The implementation uses stevedore to load both, import and optional
flows, and chains them using linear and unordered flows where needed.
DocImpact
Co-Authored: Erno Kuvaja <jokke@hp.com>
Partially-implements blueprint: new-upload-workflow
Partially-implements blueprint: introspection-of-images
Change-Id: I9e7505d4e84aabf9d71e03c360514ac824ea84de
5dd82abb74