Moving a subtask to a new Parent calls too many re-indexes on Lucene.

Reindex in Lucene is a performance bottleneck.

When we move a subtask to a new parent it re-indexes the subtask 3 times in the one operation:
1) When we remove the link to the old parent
2) When we create the link to the new parrent.
3) When we update the issue for the (possibly changed) security level.