ensure besselink does not switch sign of slip value it modifies.
ensure besselink does not switch sign of slip value it modifies.

projectchrono/chrono,Bryan-Peterson/chrono,jcmadsen/chrono,andrewseidl/chrono,andrewseidl/chrono,Bryan-Peterson/chrono,rserban/chrono,tjolsen/chrono,tjolsen/chrono,rserban/chrono,dariomangoni/chrono,armanpazouki/chrono,jcmadsen/chrono,rserban/chrono,rserban/chrono,projectchrono/chrono,rserban/chrono,projectchrono/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,Bryan-Peterson/chrono,andrewseidl/chrono,jcmadsen/chrono,armanpazouki/chrono,projectchrono/chrono,jcmadsen/chrono,Milad-Rakhsha/chrono,andrewseidl/chrono,projectchrono/chrono,dariomangoni/chrono,jcmadsen/chrono,jcmadsen/chrono,dariomangoni/chrono,armanpazouki/chrono,rserban/chrono,Bryan-Peterson/chrono,Milad-Rakhsha/chrono,amelmquist/chrono,amelmquist/chrono,Milad-Rakhsha/chrono,armanpazouki/chrono,armanpazouki/chrono,amelmquist/chrono,tjolsen/chrono,jcmadsen/chrono,amelmquist/chrono,dariomangoni/chrono,tjolsen/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,armanpazouki/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,amelmquist/chrono,tjolsen/chrono,Bryan-Peterson/chrono,amelmquist/chrono,andrewseidl/chrono,rserban/chrono