acceptance: disallow duplicate networks.
acceptance: disallow duplicate networks.

There appears to be a bug which causes Docker to look up a network based on
name, not by ID. Consequently, if multiple networks with the same name exist
(for instance due to a previous incarnation of the test crashing), it gets
confused and networking breaks down.

maxlang/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,cuongdo/cockroach,maxlang/cockroach,glycerine/cockroach,veteranlu/cockroach,veteranlu/cockroach,paperstreet/cockroach,veteranlu/cockroach,bg451/cockroach,veteranlu/cockroach,petermattis/cockroach,arjun4084346/cockroach,glycerine/cockroach,arjun4084346/cockroach,bg451/cockroach,glycerine/cockroach,sunya123/cockroach,veteranlu/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,nieyy/cockroach,sunya123/cockroach,nieyy/cockroach,bg451/cockroach,paperstreet/cockroach,bg451/cockroach,bg451/cockroach,arjun4084346/cockroach,paperstreet/cockroach,nieyy/cockroach,arjun4084346/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,sunya123/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,petermattis/cockroach,maxlang/cockroach,maxlang/cockroach,glycerine/cockroach,petermattis/cockroach,cuongdo/cockroach,nieyy/cockroach,cockroachdb/cockroach,cuongdo/cockroach,paperstreet/cockroach,cockroachdb/cockroach,sunya123/cockroach,bg451/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,petermattis/cockroach,arjun4084346/cockroach,maxlang/cockroach,vivekmenezes/cockroach,sunya123/cockroach,nieyy/cockroach,vaibhavarora/cockroach,glycerine/cockroach,glycerine/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,petermattis/cockroach,arjun4084346/cockroach,sunya123/cockroach,cockroachdb/cockroach,petermattis/cockroach,vivekmenezes/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,petermattis/cockroach,nieyy/cockroach,maxlang/cockroach,nieyy/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,maxlang/cockroach,arjun4084346/cockroach,sunya123/cockroach,cuongdo/cockroach,sunya123/cockroach,glycerine/cockroach,veteranlu/cockroach,paperstreet/cockroach,bg451/cockroach,maxlang/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,arjun4084346/cockroach,cuongdo/cockroach,vivekmenezes/cockroach,glycerine/cockroach,paperstreet/cockroach,nieyy/cockroach,petermattis/cockroach