test_compressgraph: Fix --workers parametrization and reduce number of parameters
this test takes 12s to run of Jenkins, this saves 30s in addition to the gains of actually providing --workers with a >1 value in most instances
Staging instance, all changes can be removed at any time
this test takes 12s to run of Jenkins, this saves 30s in addition to the gains of actually providing --workers with a >1 value in most instances