cmd/go: set GOWORK=off explicitly in script tests that cd to GOROOT

Some folks working on the Go project may have a go.work file in
GOROOT/src in order to test changes in x repos. 'go test cmd/go'
should not fail if that is the case.

For #58767.

Change-Id: I0e57b15fb1d3e4abc4903c177434626c9f125cae
Reviewed-on: https://go-review.googlesource.com/c/go/+/471601
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/go/testdata/script/list_std_vendor.txt

@@ -28,5 +28,6 @@ cmp stdout $WORK/net-deps.txt
 [!net] stop
 
 env GOPROXY=
+env GOWORK=off
 go mod why -m golang.org/x/net
 stdout '^# golang.org/x/net\nnet\ngolang.org/x/net'

src/cmd/go/testdata/script/mod_doc.txt

@@ -50,6 +50,7 @@ stderr '^doc: cannot find module providing package example.com/hello: module loo
 
 cd $GOROOT/src
 env GOFLAGS=
+env GOWORK=off
 go doc cryptobyte
 stdout '// import "golang.org/x/crypto/cryptobyte"'
 

src/cmd/go/testdata/script/mod_list_std.txt

@@ -36,6 +36,7 @@ stdout ^bytes$
 # rules).
 
 cd $GOROOT/src
+env GOWORK=off
 
 go list std
 stdout ^vendor/golang.org/x/net/http2/hpack