HLT Validation VBFHbb ZnnHbb bug fix

After checking the plots with more events, two fixes made:
- The VBFHbb jet pt1 efficiency plot wasn't made before, which is now fixed.
- A small bug fix for the ZnnHbb eta and phi trigger dependent histograms.

The differences can be seen here:
-- Fixed version:  /afs/cern.ch/user/j/jlauwers/public/DQM/DQM_ZnnHbb_VBFHbb_fixed.root
-- Old version: /afs/cern.ch/user/j/jlauwers/public/DQM/DQM_ZnnHbb_VBFHbb.root

The second commit removes the no longer used pre b-tagging sequence from the test code.

cc: @HuguesBrun, @slehti, @silviodonato