engine: Removal of code related to importing SAN storage domains

This patch removes code which is related to deprecated
import SAN storage domain.

Change-Id: I239c9de48084a99467d6dc06762412775db6aaca
Bug-Url: https://bugzilla.redhat.com/869142
Signed-off-by: Asaf Shakarchi <asaf@redhat.com>