jython: prevent multiple simutanious halt requests
Scan data point: Increased a store size from 5 to 300 to fix an issue
where the plot tree looses old scans.
Corba: change made by PG however I don't remember why other than it was
important.
Merge commit 'a047a7a7ec9410a6d9f26bf5557ef2c7c59537b2'
Merge commit '0231ceb537e3bee4c0de86f273115fb7a440a8da'