Revert "Only perturb padded tick marks for rectilinear axes"

This reverts commit 19777769f5c2ec586cdbf551b5d0d6e871760356.
Assume pixel distance=0 if nan

The function _get_pixel_distance_along_axis does not work for geographic
axes, in which pixels that are outside of the map area cannot be
meaningfully transformed back to data coordinates. If the return value
was nan, set to 0.