core: add vm from snapshot revert flow

The behaviour was changed when applying the revert flow to import vm
template command, there are few issues in that flow (some related and
some are not) - i'm currently applying the previous behaviour and will
reapply that change after all issues are solved - there's gonna be a
whole design change in that area, so meanwhile just applying the
previous logic.

Change-Id: Icdaed44a09f712fa0a6a4c1f5b5890f0c9c4f7a9
Signed-off-by: Liron Aravot <laravot@redhat.com>