unix: fix Test{Fd,}Xattr failure on NetBSD

On NetBSD the namespace of an xattr is stored separately from the name
and isn't returned by Listxattr and Flistxattr. Like on FreeBSD, strip
the namespace before checking the returned xattrs.

Fixes golang/go#69313
Fixes golang/go#69314

Change-Id: I7f2393cc63f9860332c0e07a51f3b9d32911e892
Cq-Include-Trybots: luci.golang.try:x_sys-gotip-netbsd-arm64
Reviewed-on: https://go-review.googlesource.com/c/sys/+/611695
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

Author: tklauser

unix/xattr_test.go

@@ -56,20 +56,22 @@ func TestXattr(t *testing.T) {
 	xattrs := stringsFromByteSlice(buf[:read])
 
 	xattrWant := xattrName
-	if runtime.GOOS == "freebsd" {
-		// On FreeBSD, the namespace is stored separately from the xattr
+	switch runtime.GOOS {
+	case "freebsd", "netbsd":
+		// On FreeBSD and NetBSD, the namespace is stored separately from the xattr
 		// name and Listxattr doesn't return the namespace prefix.
 		xattrWant = strings.TrimPrefix(xattrWant, "user.")
 	}
 	found := false
 	for _, name := range xattrs {
 		if name == xattrWant {
 			found = true
+			break
 		}
 	}
 
 	if !found {
-		t.Errorf("Listxattr did not return previously set attribute '%s'", xattrName)
+		t.Errorf("Listxattr did not return previously set attribute %q in attributes %v", xattrName, xattrs)
 	}
 
 	// find size
@@ -162,20 +164,22 @@ func TestFdXattr(t *testing.T) {
 	xattrs := stringsFromByteSlice(buf[:read])
 
 	xattrWant := xattrName
-	if runtime.GOOS == "freebsd" {
-		// On FreeBSD, the namespace is stored separately from the xattr
+	switch runtime.GOOS {
+	case "freebsd", "netbsd":
+		// On FreeBSD and NetBSD, the namespace is stored separately from the xattr
 		// name and Listxattr doesn't return the namespace prefix.
 		xattrWant = strings.TrimPrefix(xattrWant, "user.")
 	}
 	found := false
 	for _, name := range xattrs {
 		if name == xattrWant {
 			found = true
+			break
 		}
 	}
 
 	if !found {
-		t.Errorf("Flistxattr did not return previously set attribute '%s'", xattrName)
+		t.Errorf("Flistxattr did not return previously set attribute %q in attributes %v", xattrName, xattrs)
 	}
 
 	// find size