[networking] trunk: Do not have space inside --subport value
[networking] trunk: Do not have space inside --subport value

This commit also clarifies the name of trunk and related ports,
and use names in the command lines if possible.

Change-Id: If8695a9703cd384ee2a7a728a8b01d27a548e068
Closes-Bug: #1692884

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals