Allow balancing moves to introduce N+1 errors

This patch switches the applyMove function to the extended versions of
Node.addPri and addSec, and passes the override flag based on the state
of the node that we're moving away from.

Ganeti/HTools/Cluster.hs

@@ -289,8 +289,9 @@ applyMove nl inst Failover =
         old_s = Container.find old_sdx nl
         int_p = Node.removePri old_p inst
         int_s = Node.removeSec old_s inst
+        force_p = Node.offline old_p
         new_nl = do -- Maybe monad
-          new_p <- Node.addPri int_s inst
+          new_p <- Node.addPriEx force_p int_s inst
           new_s <- Node.addSec int_p inst old_sdx
           let new_inst = Instance.setBoth inst old_sdx old_pdx
           return (Container.addTwo old_pdx new_s old_sdx new_p nl,
@@ -306,13 +307,14 @@ applyMove nl inst (ReplacePrimary new_pdx) =
         tgt_n = Container.find new_pdx nl
         int_p = Node.removePri old_p inst
         int_s = Node.removeSec old_s inst
+        force_p = Node.offline old_p
         new_nl = do -- Maybe monad
           -- check that the current secondary can host the instance
           -- during the migration
-          tmp_s <- Node.addPri int_s inst
+          tmp_s <- Node.addPriEx force_p int_s inst
           let tmp_s' = Node.removePri tmp_s inst
-          new_p <- Node.addPri tgt_n inst
-          new_s <- Node.addSec tmp_s' inst new_pdx
+          new_p <- Node.addPriEx force_p tgt_n inst
+          new_s <- Node.addSecEx force_p tmp_s' inst new_pdx
           let new_inst = Instance.setPri inst new_pdx
           return (Container.add new_pdx new_p $
                   Container.addTwo old_pdx int_p old_sdx new_s nl,
@@ -326,8 +328,9 @@ applyMove nl inst (ReplaceSecondary new_sdx) =
         old_s = Container.find old_sdx nl
         tgt_n = Container.find new_sdx nl
         int_s = Node.removeSec old_s inst
+        force_s = Node.offline old_s
         new_inst = Instance.setSec inst new_sdx
-        new_nl = Node.addSec tgt_n inst old_pdx >>=
+        new_nl = Node.addSecEx force_s tgt_n inst old_pdx >>=
                  \new_s -> return (Container.addTwo new_sdx
                                    new_s old_sdx int_s nl,
                                    new_inst, old_pdx, new_sdx)
@@ -342,9 +345,10 @@ applyMove nl inst (ReplaceAndFailover new_pdx) =
         tgt_n = Container.find new_pdx nl
         int_p = Node.removePri old_p inst
         int_s = Node.removeSec old_s inst
+        force_s = Node.offline old_s
         new_nl = do -- Maybe monad
           new_p <- Node.addPri tgt_n inst
-          new_s <- Node.addSec int_p inst new_pdx
+          new_s <- Node.addSecEx force_s int_p inst new_pdx
           let new_inst = Instance.setBoth inst new_pdx old_pdx
           return (Container.add new_pdx new_p $
                   Container.addTwo old_pdx new_s old_sdx int_s nl,
@@ -360,9 +364,10 @@ applyMove nl inst (FailoverAndReplace new_sdx) =
         tgt_n = Container.find new_sdx nl
         int_p = Node.removePri old_p inst
         int_s = Node.removeSec old_s inst
+        force_p = Node.offline old_p
         new_nl = do -- Maybe monad
-          new_p <- Node.addPri int_s inst
-          new_s <- Node.addSec tgt_n inst old_sdx
+          new_p <- Node.addPriEx force_p int_s inst
+          new_s <- Node.addSecEx force_p tgt_n inst old_sdx
           let new_inst = Instance.setBoth inst old_sdx new_sdx
           return (Container.add new_sdx new_s $
                   Container.addTwo old_sdx new_p old_pdx int_p nl,