support 'loopback' as a device type.

As reported in bug 1671927, sysconfig had an issue with rendering
a loopback device.  The problem was that some as yet unknown issue was
causing the openstack config drive to parse the provided ENI file rather
than reading the network_data.json.  Parsing an ENI file would add a
a 'lo' device of type 'physical', and sysconfig was failing to render
that.

The change here is:
 a.) add a 'loopback' type rather than 'physical' for network config.
     {'name': 'lo', 'type': 'loopback', 'subnets': ['type': 'loopback']}
 b.) support skipping that type in the eni and sysconfig renderers.
 c.) make network_state just piggy back on 'physical' renderer for
     loopback (this was what was happening before).

Tests are added for eni and sysconfig renderer.

1 files changed, 4 insertions, 0 deletions

diff --git a/cloudinit/net/network_state.py b/cloudinit/net/network_state.py
index 11ef585b..90b2835a 100644
--- a/cloudinit/net/network_state.py
+++ b/cloudinit/net/network_state.py
@@ -212,6 +212,10 @@ class NetworkStateInterpreter(object):
                     LOG.debug(self.dump_network_state())
 
     @ensure_command_keys(['name'])
+    def handle_loopback(self, command):
+        return self.handle_physical(command)
+
+    @ensure_command_keys(['name'])
     def handle_physical(self, command):
         '''
         command = {