Fix sign of the tgL in ITS seeding

[shahor02]

@f3sch The tgl sign indeed must be inverted, currently it always flips from seeding to cell fit.

 [3651609:its-tracker]: seed: X:+3.8122e+00 Alp:-1.075e+00 Par: +9.7989e-01 +1.1784e+00 +2.6474e-01 -8.9826e-01 -2.8998e+00 |Q|:1 Pion
[3651609:its-tracker]: fit:: X:+2.1876e+00 Alp:-1.069e+00 Par: +5.2618e-01 -3.3599e-01 +2.5181e-01 +8.9755e-01 -2.8725e+00 |Q|:1 Pion

We did not see a particular effect since the direct seeding with the wrong sign (inward clusters fit) is used only at cell building (no linRef used). And for the seeding in the reverse order, the tgL sign was correct by accident.

[f3sch]

Ah ok, understood now, thanks!
I see tracks shifting very slightly shifting to 6 clusters long, and less 4 cluster tracks: