ssh/terminal: consistent return value for Restore

This patch makes the Restore function return nil
on success to be consistent with other functions
like MakeRaw.

Change-Id: I81e63f568787dd88466a5bb30cb87c4c3be75a5c
Reviewed-on: https://go-review.googlesource.com/34952
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ssh/terminal/util.go

@@ -72,8 +72,10 @@ func GetState(fd int) (*State, error) {
 // Restore restores the terminal connected to the given file descriptor to a
 // previous state.
 func Restore(fd int, state *State) error {
-	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&state.termios)), 0, 0, 0)
-	return err
+	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&state.termios)), 0, 0, 0); err != 0 {
+		return err
+	}
+	return nil
 }
 
 // GetSize returns the dimensions of the given terminal.