HP cloud avl zones

HP compute avl zones were hardcoded to assume that the first response is for az-1, then az-2 (and not support for az-3). Change this to look up the avl zone based on the passed in zone string. The passed in avl zones should now be strings of the form "az-1", "az-2", etc, as opposed to symbols that are currently used. This also adds support for the new zone, az-3, for free.