os: don't return Chmod's error from Mkdir and OpenFile

Mkdir and OpenFile call Chmod internally on *BSD and Solaris,
because these OSes don't handle the sticky bit correctly.

However Chmod's error should be ignored. It shouldn't hide
the fact that a file itself is created.

Fixes #8383

Change-Id: Ia2e0b2ba72712d73a0a48ba5a263432e0fff31a5
Reviewed-on: https://go-review.googlesource.com/2057
Reviewed-by: Russ Cox <rsc@golang.org>

src/os/file.go

@@ -204,14 +204,15 @@ func (f *File) WriteString(s string) (ret int, err error) {
 func Mkdir(name string, perm FileMode) error {
 	e := syscall.Mkdir(name, syscallMode(perm))
 
-	// mkdir(2) itself won't handle the sticky bit on *BSD and Solaris
-	if !supportsCreateWithStickyBit && e == nil && perm&ModeSticky != 0 {
-		e = Chmod(name, perm)
-	}
-
 	if e != nil {
 		return &PathError{"mkdir", name, e}
 	}
+
+	// mkdir(2) itself won't handle the sticky bit on *BSD and Solaris
+	if !supportsCreateWithStickyBit && perm&ModeSticky != 0 {
+		Chmod(name, perm)
+	}
+
 	return nil
 }
 

src/os/file_unix.go

@@ -88,8 +88,8 @@ func OpenFile(name string, flag int, perm FileMode) (file *File, err error) {
 	}
 
 	// open(2) itself won't handle the sticky bit on *BSD and Solaris
-	if chmod && e == nil {
-		e = Chmod(name, perm)
+	if chmod {
+		Chmod(name, perm)
 	}
 
 	// There's a race here with fork/exec, which we are