Copy policy_add() from Grenade functions

policy_all() was added to Grenade's functions file, which is notmally synced
from DevStack so we need to bring it over here before the next sync.

Change-Id: Ifd852e9d1ffe39fa23f6312d1ddf2874b5f2b9f0
Merge "Copy policy_add() from Grenade functions"