os.MkdirAll creates directory before umask so make sure that a desired
permission is set after creating a directory with MkdirAll. Use the
existing TouchDirAll function which checks for permission if dir is already
exist and when create a new dir.
pkg/ is a collection of utility packages used by etcd without being specific to etcd itself. A package belongs here
only if it could possibly be moved out into its own repository in the future.