Fix spelling of OpenStack

According to the OpenStack Documentation conventions it should
be OpenStack and not Openstack or openstack.

https://wiki.openstack.org/wiki/Documentation/Conventions#OpenStack.2C_not_Openstack_or_openstack

Change-Id: I08a0432dd00a122a4e335f9af0577892737cd64d
Merge "Fix spelling of OpenStack"