Add support for cloud-init on LXC instances

Images that use cloud-init are not correctly initialized when using
libvirt LXC nova driver.

One way cloud-init checks if the OpenStack datasource should be used
is by checking DMI data that is meaningful for virtual machines but
not for containers.

Another way cloud-init is using is to check if the 'product_name'
env variable for init process (PID 1) is "OpenStack Nova" [1][2].

This commit add that env variable to the instance when the driver
is LXC.

[1] https://cloudinit.readthedocs.io/en/latest/topics/datasources/openstack.html
[2] https://git.launchpad.net/cloud-init/tree/tools/ds-identify#n974

Closes-Bug: 1834506

Change-Id: I2d0a4461081f5284d16df73a783cb7dae3ff0ef5
Signed-off-by: Miguel Herranz <miguel@midokura.com>

nova/tests/unit/virt/libvirt/test_driver.py

@@ -2414,6 +2414,7 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         self.assertEqual("/sbin/init", cfg.os_init_path)
         self.assertEqual("console=tty0 console=ttyS0 console=hvc0",
                          cfg.os_cmdline)
+        self.assertEqual("OpenStack Nova", cfg.os_init_env['product_name'])
         self.assertIsNone(cfg.os_root)
         self.assertEqual(3, len(cfg.devices))
         self.assertIsInstance(cfg.devices[0],
@@ -8665,6 +8666,8 @@ class LibvirtConnTestCase(test.NoDBTestCase,
         check = [
             (lambda t: t.find('.').get('type'), 'lxc'),
             (lambda t: t.find('./os/type').text, 'exe'),
+            (lambda t: t.find("./os/initenv[@name='product_name']").text,
+                    'OpenStack Nova'),
             (lambda t: t.find('./devices/filesystem/target').get('dir'), '/')]
 
         for i, (check, expected_result) in enumerate(check):

nova/virt/libvirt/driver.py

@@ -5068,6 +5068,7 @@ class LibvirtDriver(driver.ComputeDriver):
         elif virt_type == "lxc":
             guest.os_init_path = "/sbin/init"
             guest.os_cmdline = CONSOLE
+            guest.os_init_env["product_name"] = "OpenStack Nova"
         elif virt_type == "uml":
             guest.os_kernel = "/usr/bin/linux"
             guest.os_root = root_device_name

releasenotes/notes/bug-1834506-7c6875bbdc32ab0b.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    LXC instances now support cloud-init.