Redo the vacukming process to mkake it scalable.

Redo the vacukming process to mkake it scalable.

Vacumming used to delete one record at a time on all nodes, that was
m*n behaviour and would require a huge storm of ctdb->ctdb controls and just wouldnt scale at all.

The new vacuming process collects all records to be deleted locally and then only sends 1 control to the other nodes. This control contains a list of all records to be deleted.