Fix bug in finding shell
Fix bug in finding shell

chenrui2014/dockersh,Yelp/dockersh,mehulsbhatt/dockersh,CS497-F15/dockersh,Yelp/dockersh,CS497-F15/dockersh,pugna0/dockersh,beni55/dockersh,beni55/dockersh,mehulsbhatt/dockersh,pugna0/dockersh,chenrui2014/dockersh