In the list of involved nodes, drop "no secondary"

When grouping moves into jobs, a new job set is started, if the new
move involves a node also touched by a previous move. When computing
the list of involved nodes, the new primary and secondary nodes of the
instance are included; if an instance, however, has only one node, the
"no secondary" index -1 should be left out to avoid spurious conflicts
between unrelated moves of single-homed instances.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Hrvoje Ribicic <riba@google.com>

src/Ganeti/HTools/Cluster.hs

@@ -1410,7 +1410,7 @@ involvedNodes :: Instance.List -- ^ Instance list, used for retrieving
 involvedNodes il plc =
   let (i, np, ns, _, _) = plc
       inst = Container.find i il
-  in nub $ [np, ns] ++ Instance.allNodes inst
+  in nub . filter (>= 0) $ [np, ns] ++ Instance.allNodes inst
 
 -- | Inner function for splitJobs, that either appends the next job to
 -- the current jobset, or starts a new jobset.