Removing a linked output file in a service, makes the next service unrunnable without clear reason

[sanderegg]

• create 2 connected sleepers services

• run the computation

• select the first sleeper and go to outputs service data

• delete the single_number.txt output
  --> the service is not shown as modified, still shows success

• try running the second sleeper by selecting and hitting run selection
  --> Fails
  --> No information why

Needed changes

• when the file is deleted in the first sleeper, the director-v2 is unaware of it and therefore does not recompute the state of the service
• Fixing this should fix the issue