copy.Image(): select the CopySystemImage image using the source context
copy.Image(): select the CopySystemImage image using the source context

Go back to selecting which image instance we copy in CopySystemImage
mode using the source context rather than the destination context.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

containers/image,containers/image