Speed up DocumentDiscoveryLiteServiceTest

Currently the DocumentDiscoveryLiteServiceTest takes about 40-60sec - this would ideally be reduced to speed up the whole unit test part.

• testLargeStartStopFiesta is the largest one with 17sec
• perhaps using virtual clock instead of real clock could be an approach
  • or make two variants: one for the ITs that uses real clock and one for the unit tests that uses virtual clocks..