Document network trunk commands

Commands were added for network trunk object as part of
change I6fe1dbd81813fae234801a61c0e3d89f9e7c791e.
This patch adds documentation for the same.

Change-Id: If89478bb4b8af08de11ad521669ba2ee91b76f69
Partial-implements: blueprint vlan-aware-vms

Author: abhiraut

doc/source/commands.rst

@@ -178,6 +178,8 @@ list check out :doc:`plugin-commands`.
 * ``dataprocessing plugin``: (**Data Processing (Sahara)**)
 * ``message-broker cluster``: (**Message Broker (Cue)**)
 * ``message flavor``: (**Messaging (Zaqar)**)
+* ``network subport``: (**Networking (Neutron)**)
+* ``network trunk``: (**Networking (Neutron)**)
 * ``orchestration resource``: (**Orchestration (Heat)**)
 * ``orchestration template``: (**Orchestration (Heat)**)
 * ``pool``: (**Messaging (Zaqar)**)