Small bugfix in TrackJets overlap removal of SUSYTools

Hi @ykeisuke, @oabouzei,

happy new year first of all. During a chat with @pgadow, I noticed that the new feature of the track jet overlap removal has a small bug in it, since the dR is calcutaed via

dR^{2} = (eta1 - eta2)^{2} + (phi1 -phi2)^{2};

if jet1 one has phi of pi + depsilon and the oher -phi-depsilon, then the equation above gives roughly 2pi. I also switched from using the auto loop to the iterators directly since this allows us to avoid pairing the jets twice.

I include @schae, @jgonski to this request to have a final pairs of eyes look at this small fix.

Cheers,

Johannes