ConfigDrive: write 'injected' files and legacy networking

Previous commit disabled the consumption of 'injected' files in 
configdrive (openstack server boot --file=/target/file=local-file)
unless the datasource was in 'pass' mode.  The default mode is 'net'
so that would never happen.

Also here are:
a.) a fix for 'links_path_prefix' string from debian, to finally
    disable the rendering of systemd.link files (LP: #1594546)
b.) some comments to apply_network_config
c.) implement a backwards compatibility for for distros that do
    not yet implement apply_network_config by converting the network
    config into ENI format and calling apply_network.

    This is required because prior to the previous commit, those distros
    would have had 'apply_network' called with the openstack provided
    ENI file.  But after this change they will have apply_network_config
    called by cloudinit's main.
d.) a network_state_to_eni helper for converting net config to eni
    it supports the not-actually-correct 'hwaddress' field in ENI.

LP: #1602373

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index 3ae00fc6..6f4dad13 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -269,6 +269,37 @@ iface eth1000 inet dhcp
         self.assertEqual(expected.lstrip(), contents.lstrip())
 
 
+class TestEniNetworkStateToEni(TestCase):
+    mycfg = {
+        'config': [{"type": "physical", "name": "eth0",
+                    "mac_address": "c0:d6:9f:2c:e8:80",
+                    "subnets": [{"type": "dhcp"}]}],
+        'version': 1}
+    my_mac = 'c0:d6:9f:2c:e8:80'
+
+    def test_no_header(self):
+        rendered = eni.network_state_to_eni(
+            network_state=network_state.parse_net_config_data(self.mycfg),
+            render_hwaddress=True)
+        self.assertIn(self.my_mac, rendered)
+        self.assertIn("hwaddress", rendered)
+
+    def test_with_header(self):
+        header = "# hello world\n"
+        rendered = eni.network_state_to_eni(
+            network_state=network_state.parse_net_config_data(self.mycfg),
+            header=header, render_hwaddress=True)
+        self.assertIn(header, rendered)
+        self.assertIn(self.my_mac, rendered)
+
+    def test_no_hwaddress(self):
+        rendered = eni.network_state_to_eni(
+            network_state=network_state.parse_net_config_data(self.mycfg),
+            render_hwaddress=False)
+        self.assertNotIn(self.my_mac, rendered)
+        self.assertNotIn("hwaddress", rendered)
+
+
 class TestCmdlineConfigParsing(TestCase):
     simple_cfg = {
         'config': [{"type": "physical", "name": "eth0",