Job De-duplication

[stephan271]

Issue Name

JobDeduplication

Summary

It should not be possible to create the same job from the same user more than once in a short time period

Current Behaviour

Identical Jobs (e.g. retrieve jobs) can be triggered arbitrarily often causing problems in the tape backend

Expected Behaviour

Another job request with identical data is ignored within a certain time window (1 to 10 Minutes)