Mostly revert "FlatLatticeTiling: fix bug in setting parameter-space bounds"

- This mostly reverts commit 53dcdaf41ecc9abe579854e50abf9c5a938e2fb0
- Forcing the tiling state to change when getting bounds is not a good
  idea after all: means bounds cannot be computed independently while
  tiling is in use, e.g. for generating random points in parameter space
- Instead, just fix the copy-and-paste bugs in XLALNextFlatLatticePoint()