Run opx installation in screen session
Run opx installation in screen session

opx-nas-interface postinst is breaking the ssh connection. Detach when
installing to get around this.

Change-Id: I29b8e54564c7213715859eeb52b7dadd4ed49c7d
Signed-off-by: Tyler Heucke <7d5279c5bf9085ad0457cbc11f4d8b77130c8ffa@dell.com>

open-switch/infra_project-config,open-switch/infra_project-config