Avoid duplicated project_id when show network

Project_id appear twice when show network. This
patch check and not append if it already has one.

Change-Id: I4400239f454522101b639a0412050dd60eb6a612
Closes-Bug: #1636123
Partially-Implements: blueprint duplicated-project-id

openstackclient/network/v2/network.py

@@ -42,6 +42,7 @@ def _get_columns(item):
     columns = list(item.keys())
     if 'tenant_id' in columns:
         columns.remove('tenant_id')
+    if 'project_id' not in columns:
         columns.append('project_id')
     return tuple(sorted(columns))