Code review: 6821084:  Small fix to the preprocessing library [path issues again].
Code review: 6821084:  Small fix to the preprocessing library [path issues again].

kiddinn/plaso,Onager/plaso,rgayon/plaso,log2timeline/plaso,log2timeline/plaso,kiddinn/plaso,Onager/plaso,kiddinn/plaso,joachimmetz/plaso,rgayon/plaso,joachimmetz/plaso,rgayon/plaso