Fixes possible dirty server version read upon client connection

* TeiidServer
 * Since the teiid version is crucial to both the initialising and
   refreshing of the ExecutionAdmin component, it must be correct prior
   to its assignment.
 * Queries and sets the teiid version prior to any initialising of admin

* Admin8Factory
 * Stops caching of the factories since this is unnecessary
 * Moves version state into the AdminImpl where it is required.
 * Since lacks any other state, becomes a singleton.