os/user: simplify skipping listGroups test

This is not implemented on AIX and Illumos, and we already have a
mechanism to skip the test case -- let's use it.

Change-Id: Idb1cc2d716cf6d0731e93dfc3aa7853b9edec41f
Reviewed-on: https://go-review.googlesource.com/c/go/+/330752
Reviewed-by: Tobias Klauser <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Run-TryBot: Tobias Klauser <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: kolyshkin

src/os/user/listgroups_aix.go

@@ -9,6 +9,12 @@ package user
 
 import "fmt"
 
+// Not implemented on AIX, see golang.org/issue/30563.
+
+func init() {
+	groupListImplemented = false
+}
+
 func listGroups(u *User) ([]string, error) {
 	return nil, fmt.Errorf("user: list groups for %s: not supported on AIX", u.Username)
 }

src/os/user/listgroups_illumos.go

@@ -13,6 +13,12 @@ package user
 
 import "fmt"
 
+// Not implemented on illumos, see golang.org/issue/14709.
+
+func init() {
+	groupListImplemented = false
+}
+
 func listGroups(u *User) ([]string, error) {
 	return nil, fmt.Errorf("user: list groups for %s: not supported on illumos", u.Username)
 }

src/os/user/user_test.go

@@ -5,7 +5,6 @@
 package user
 
 import (
-	"runtime"
 	"testing"
 )
 
@@ -128,12 +127,6 @@ func checkGroupList(t *testing.T) {
 
 func TestGroupIds(t *testing.T) {
 	checkGroupList(t)
-	if runtime.GOOS == "aix" {
-		t.Skip("skipping GroupIds, see golang.org/issue/30563")
-	}
-	if runtime.GOOS == "illumos" {
-		t.Skip("skipping GroupIds, see golang.org/issue/14709")
-	}
 	user, err := Current()
 	if err != nil {
 		t.Fatalf("Current(): %v", err)