Fix create execution when workbook does not exist

 * Controller return 404 Not Found if Workbook doesn't exist
   or workbook definition is empty (in case of empty
   Definition we can't start Execution)

Closes-bug: #1325914

Change-Id: I5ae18d378916c6eba81088603414300891f1b816
Merge "Fix create execution when workbook does not exist"