The jobgeneration of Snapshot harvests using the DefaultJobGenerator.java generates too many jobs

Recently TLR initiated a Step 2 snapshot harvest at Netarkivet.
This generated a total of 2099 jobs.

The most recent Step 2 snapshot harvest generated only 647 jobs.

In the mean time, we have introduced extended attributes to our domainconfigurations, making the selection of domainconfigs during the jobgeneration-phase more complex.

We already made some fixes before releasing NetarchiveSuite 5.1 (https://sbforge.org/display/NAS/NetarchiveSuite+5.1+Release+Notes, where issue NAS-2499 (and duplicate NAS-2497) was resolved