Move overcloud package version swap/dependency closer to where it's needed/used

[jbemmel]

At https://github.com/nuagenetworks/nuage-ospdirector/tree/OSPD13/Documentation/5.4.1#phase-1-install-red-hat-openstack-platform-director there is a step to 'swap' the overcloud templates to a specific version.

However, this dependency isn't used until phase 5: https://github.com/nuagenetworks/nuage-ospdirector/tree/OSPD13/Documentation/5.4.1#phase-5-deploy-the-overcloud

To improve the workflow and to accomodate users who might skip ahead, it would be better to move the 'swap' step to phase 5 (just before running overcloud deploy)