fixing ipSigLeadTrk retrieval for offline taus for Run3 TauMonitoring
After this MR :
by @martindl, update retrieving of "ipSigLeadTrk" variable for offline taus also for Run3 TauMonitoring. Same mechanism won't work for online taus since "d0SigTJVA
" still not existing for HLT TauTrack and this will be investigated
Edited by Antonio De Maria