Set the port to use oslo_config PortOpt
Set the port to use oslo_config PortOpt

Since oslo_config has already supported PortOpt,
let's use the new type for port options.

And add help for file_server.

Change-Id: Id03c33e6200fe8bddce2e754df35e74e82e60b1e
Depends-On: Ida294b05a85f5bef587b761fcd03c28c7a3474d8
Closes-Bug: #1508792

satish-avninetworks/murano,olivierlemasle/murano,NeCTAR-RC/murano,NeCTAR-RC/murano,satish-avninetworks/murano,DavidPurcell/murano_temp,DavidPurcell/murano_temp,DavidPurcell/murano_temp,satish-avninetworks/murano,NeCTAR-RC/murano,olivierlemasle/murano,NeCTAR-RC/murano,satish-avninetworks/murano,olivierlemasle/murano,olivierlemasle/murano,DavidPurcell/murano_temp,openstack/murano,openstack/murano