ipfilter userland: Path fixup no longer required

Since the move of ipfilter from contrib to sbin adjusting the source path
is no longer required.

Fixes: 41edb306f05651fcaf6c74f9e3557f59f80292e1

(cherry picked from commit 7cb2d7c41368a662bb5e8db5e12420d4a8a190b1)