Update to Havana 2013.2 release

* Use epoch to make 2013.2 newer than 2013.2.rc2
* New dependency python2-pytz

Signed-off-by: Lance Chen <cyen0312@gmail.com>
Move nova.install into nova-common package

Actions in nova.install should only be run in one of the packages

Signed-off-by: Lance Chen <cyen0312@gmail.com>
New dependecy libvirt-python

libvirt python binding has been separated from version 1.2.0

Signed-off-by: Lance Chen <cyen0312@gmail.com>