Small enhancement for MONDRIAN-1282. When dealing with interrupted queries, we have to temporarely remove the thread interruption flag so that we can send a message to the server monitor, or else it fails while placing a message in the monitor's actor message queue.
Merge of ede12851a34b315257375e1378c509c5340d3432 from master.
Removes the closing of statements from the monitoring threads. Only cancelations should be processed that way. The actual close operation must be delayed until the call to cancel gets seen by the SQL thread, or else the connection gets placed back into the pool and then all sorts of thread safety problems happen.

Conflicts:

	src/main/mondrian/server/Execution.java