add fixed-ref comparison to q445, reduces list of excluded branches

For test_q445, adding a comparison against the nightly of June 11 in order to accompany !54259 (closed).

Also removing some --ignore-leaves in a few other tests following resolution of ATR-25521.

Also printing the contents of the /cvmfs/....../version.txt file (in test_bulkProcessing_900collisions_SB) to identify which reference is used.