ssh/terminal: fix line endings handling in ReadPassword Fixes golang/go#16552 Change-Id: I18a9c9b42fe042c4871b3efb3f51bef7cca335d0 Reviewed-on: https://go-review.googlesource.com/25355 Reviewed-by: Adam Langley <alangley@gmail.com> Reviewed-by: Adam Langley <agl@golang.org>