Make the installation work offline (disconnected install)

[nmasse-itix]

OpenShift disconnected install is described here :
https://docs.openshift.com/container-platform/3.6/install_config/install/disconnected_install.html

However, it is not documented for 3scale and RH-SSO

[nmasse-itix]

TODO: 3scale 2.1 needs to have their imagePullPolicy changed from always to IfNotPresent.