Try again to fix the inter-cluster move QA test

This time, we re-establish the old pri/sec nodes corretly. Unfortunately this
will require now a 3-node cluster at least for drbd instances, hence it's
somewhat suboptimal, but… The other option would be to move it simply from p:s
to s:p and then back to p:s, without involving a third node (for DRBD case),
but I think that moving it to a completely separate node is slightly better for
testing.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>