Change back to using vpn_agent.ini

After https://review.openstack.org/#/c/555167/ merged
downstream packaging jobs broke due to the filename
change to l3_agent.ini.  Change it back to vpn_agent.ini
since it could cause an upgrade issue.

Also, since l3_agent.ini is already used in the neutron
tree, having a file with the same name could cause some
confusion, so it's better to use something unique.

Change-Id: I39cf2c0d1c54e7c292dcdf71831c1a3cbc67284a

doc/source/conf.py

@@ -246,7 +246,7 @@ bug_tag = 'doc'
 # -- Options for oslo_config.sphinxconfiggen ---------------------------------
 
 _config_generator_config_files = [
-    'l3_agent.ini',
+    'vpn_agent.ini',
     'neutron_vpnaas.conf',
 ]
 

doc/source/configuration/l3_agent.rst

@@ -1,6 +1,9 @@
-============
+=============
-l3_agent.ini
+vpn_agent.ini
-============
+=============
+
+This is a configuration file for the VPNaaS L3 agent
+extension of the neutron l3-agent.
 
 .. show-options::
-   :config-file: etc/oslo-config-generator/l3_agent.ini
+   :config-file: etc/oslo-config-generator/vpn_agent.ini

doc/source/configuration/samples/l3_agent.rst

@@ -1,8 +0,0 @@
-===================
-Sample l3_agent.ini
-===================
-
-This sample configuration can also be viewed in `the raw format
-<../../_static/config_samples/l3_agent.conf.sample>`_.
-
-.. literalinclude:: ../../_static/config_samples/l3_agent.conf.sample

doc/source/configuration/samples/vpn_agent.rst

@@ -0,0 +1,8 @@
+====================
+Sample vpn_agent.ini
+====================
+
+This sample configuration can also be viewed in `the raw format
+<../../_static/config_samples/vpn_agent.conf.sample>`_.
+
+.. literalinclude:: ../../_static/config_samples/vpn_agent.conf.sample

etc/oslo-config-generator/vpn_agent.ini

@@ -1,5 +1,5 @@
 [DEFAULT]
-output_file = etc/l3_agent.ini.sample
+output_file = etc/vpn_agent.ini.sample
 wrap_width = 79
 
 namespace = neutron.vpnaas.agent