HNL beam smearing incorrect

[olantwin]

HNL smearing (2d Gaussian):

FairShip/shipgen/HNLPythia8Generator.cxx

Lines 188 to 195 in e0bd057

	if (fsmearBeam>0){
	Double_t test = fsmearBeam*fsmearBeam;
	Double_t Rsq = test+1.;
	while(Rsq>test){
	dx = gRandom->Uniform(-1.,1.) * fsmearBeam;
	dy = gRandom->Uniform(-1.,1.) * fsmearBeam;
	Rsq = dx*dx+dy*dy;
	}

MuonBack (circular smearing including beam sweep):

FairShip/shipgen/MuonBackGenerator.cxx

Lines 173 to 178 in e0bd057

	if (fsmearBeam > 0) {
	Double_t r = fsmearBeam + 0.8 * gRandom->Gaus();
	Double_t _phi = gRandom->Uniform(0., 2.) * TMath::Pi();
	dx = r * TMath::Cos(_phi);
	dy = r * TMath::Sin(_phi);
	}

Should be simple enough to correct, we should probably define this in a single place to avoid different generators getting out of sync.