Use network_mode=bridge when testing links
Use network_mode=bridge when testing links

Links are only compatible with network mode bridge.
New versions of docker only create env entries when network mode
is properly set.

Signed-off-by: Joffrey F <2e95f49799afcec0080c0aeb8813776d949e0768@docker.com>

uggla/docker-py,rancher/docker-py,minzhang28/docker-py,wlan0/docker-py,rhatdan/docker-py,youhong316/docker-py,olsaki/docker-py,bfirsh/docker-py,Faylixe/docker-py,docker/docker-py,bfirsh/docker-py,dimaspivak/docker-py,funkyfuture/docker-py,aiden0z/docker-py,aiden0z/docker-py,tbeadle/docker-py,TomasTomecek/docker-py,dimaspivak/docker-py,kaiyou/docker-py,minzhang28/docker-py,dlorenc/docker-py,funkyfuture/docker-py,auready/docker-py,ColinHuang/docker-py,kaiyou/docker-py,schu/docker-py,Faylixe/docker-py,youhong316/docker-py,ColinHuang/docker-py,docker/docker-py,vdemeester/docker-py,vdemeester/docker-py,kpavel/docker-py,mark-adams/docker-py,vpetersson/docker-py,vitalyisaev2/docker-py,vpetersson/docker-py,auready/docker-py