[Redundancy] Do not redo registration for harmonized data

[tashrifbillah]

https://github.com/pnlbwh/dMRIharmonization/blob/spm-bspline/lib/debug_fa.py#L100

Employ the same logic in the above as used here.

Should save us some time for software development (multiple run).

P.S. no question of redoing for multi-shell because it is done only once for bmax shell.