Fix N_hits issue & fill AHDC::track bank before KF

[zyzhangjlab]

1. Fix the issue that there are events with number of hits < 6.
2. fill chi2, sum_adc, path and dEdx in AHDC::track bank before Kalman Filter.

[ftouchte]

I made some review. The idea is that, if a quantity can be calculated, we should not have a setter for it.

Example: sum_adc can be directly calculated, I guess the path is set. But dEdx uses both of these information.

We should make a choice. Whether we compute everything, whether we set everything.

As a consequence, some variables are left non used.

[baltzell]

@ftouchte et.al, if you think this should be merged, please approve it.