Added new import method 'copy-image' which will copy existing image into
specified list of stores. Introduced additional task which will serve
as internal plugin which will allow copying existing image into staging
area and then this data will be uploaded to specified stores via regula
import flow.
NOTE: This new import method 'copy-image' is only supported if multiple
stores are enabled in deployment.
APIImpact
Implements: blueprint copy-existing-image
Change-Id: I13eaab7ab013f44ce18465bdbdbe8052942570ff
1754c9e2b0