Update unit test for OSG 3.5 and singularity
Tests have fixtures for OSG 3.3 sites (no more supported) and 3.4 (phasing out).
3.5 is not mentioned explicitly. So it is missing unless regular (other) entries are 3.5
Then tests were testing for GlExec enabled as special cases but are not testing for singularity enabled jobs/sites.
Singularity like GlExec affects also the matching in the Frontend