net/http: skip TestTransportClosesBodyOnError on Plan 9
net/http: skip TestTransportClosesBodyOnError on Plan 9

LGTM=rsc
R=bradfitz, rsc
CC=golang-codereviews
https://codereview.appspot.com/87800044

tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go