syscall: TestGroupCleanupUserNamespace needs additional output value

[pto]

Running the ARM version of ArchLinux, the id command is returning a slight variant of the strings listed in TestGroupCleanupUserNamespace in src/syscall/exec_linux_test.go lines 238-240. It lists "65534" but doesn't translate that to any group name.

1. What version of Go are you using (go version)?
   go version go1.7rc1 linux/arm64

2. What operating system and processor architecture are you using (go env)?
   ArchLinux ARM (kernel 3.14.65-14 on ODROID-C2)
   GOARCH="arm64"
   GOBIN=""
   GOEXE=""
   GOHOSTARCH="arm64"
   GOHOSTOS="linux"
   GOOS="linux"
   GOPATH="/home/pto/go"
   GORACE=""
   GOROOT="/usr/local/go"
   GOTOOLDIR="/usr/local/go/pkg/tool/linux_arm64"
   CC="gcc"
   GOGCCFLAGS="-fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build205812448=/tmp/go-build -gno-record-gcc-switches"
   CXX="g++"
   CGO_ENABLED="1"

3. What did you do?
   sudo go tool dist test -run syscall

4. What did you expect to see?
   ALL TESTS PASSED

5. What did you see instead?

   Testing packages.

   --- FAIL: TestGroupCleanupUserNamespace (0.00s)
   exec_linux_test.go:247: id command output: "uid=0(root) gid=0(root) groups=0(root),65534", expected one of ["uid=0(root) gid=0(root) groups=0(root)" "uid=0(root) gid=0(root) groups=0(root),65534(nobody)" "uid=0(root) gid=0(root) groups=0(root),65534(nogroup)"]
   FAIL
   FAIL syscall 0.157s
   2016/07/08 13:57:42 Failed: exit status 1

[gopherbot]

CL https://golang.org/cl/24833 mentions this issue.