The fix in #614  is kludgey.
Propose moving the change to Installation/Controller.php.
Note: requires ZF 1.5+
(In ) refs #865 - comment out unix_socket until we update ZF
(In ) refs #865 - re-worked unix_socket support for Zend_Db and Tracker_Db
Installation will now accept:
Connecting to the database, Piwik will look at the unix_socket setting (if set), or a socket path in the port; else fallback to traditional host:port.
(Note: the algorithm in  no longer depends on the ZF update.)