Updated openstack/openstack
Project: openstack-dev/devstack  78ab80e5589a7df21a03f06f38c4bae3e79bf756
null
use ext4 for guest default ephemeral

this isn't upstream default because of compatibility questions
with really old host on providers. However there is no reason not
to do it in devstack.

Change-Id: I6438c0efb297cfa5d3dbb5f00701b24f01c39d14