Fixed 'privileged' instance creation using config-drive

Exsiting config drive creation flow assume that LXD
ALWAYS return UID mapping for instance.
For privieged this is not true, as not UID mapping perfomed.
Existing code which try simply split JSON answer and
lookup in it failed as result.
Parser switched to JSON based parsing and have fallback
to zero UID if no mapping found in LXD answer.

Change-Id: If11bf72a9fdeeaff4f55cfca0ec0bc0a1bc6ce3c
Closes-Bug: 1707101

nova/virt/lxd/driver.py

@@ -1201,9 +1201,40 @@ class LXDDriver(driver.ComputeDriver):
                 format=CONF.config_drive_format)
 
         container = self.client.containers.get(instance.name)
-        container_id_map = container.config[
-            'volatile.last_state.idmap'].split(',')
-        storage_id = container_id_map[2].split(':')[1]
+        storage_id = 0
+        """
+        Determine UID shift used for container uid mapping
+        Sample JSON config from LXD
+        {
+            "volatile.apply_template": "create",
+            ...
+            "volatile.last_state.idmap": "[
+                {
+                \"Isuid\":true,
+                \"Isgid\":false,
+                \"Hostid\":100000,
+                \"Nsid\":0,
+                \"Maprange\":65536
+                },
+                {
+                \"Isuid\":false,
+                \"Isgid\":true,
+                \"Hostid\":100000,
+                \"Nsid\":0,
+                \"Maprange\":65536
+                }] ",
+            "volatile.tap5fd6808a-7b.name": "eth0"
+        }
+        """
+        container_id_map = json.loads(
+            container.config['volatile.last_state.idmap'])
+        uid_map = filter(lambda id_map: id_map.get("Isuid"), container_id_map)
+        if uid_map:
+            storage_id = uid_map[0].get("Hostid", 0)
+        else:
+            # privileged containers does not have uid/gid mapping
+            # LXD API return nothing
+            pass
 
         extra_md = {}
         if admin_password:
@@ -1249,10 +1280,12 @@ class LXDDriver(driver.ComputeDriver):
                 for ent in os.listdir(tmpdir):
                     shutil.copytree(os.path.join(tmpdir, ent),
                                     os.path.join(configdrive_dir, ent))
-                    utils.execute('chmod', '-R', '775', configdrive_dir,
-                                  run_as_root=True)
-                    utils.execute('chown', '-R', storage_id, configdrive_dir,
-                                  run_as_root=True)
+
+                utils.execute('chmod', '-R', '775', configdrive_dir,
+                              run_as_root=True)
+                utils.execute('chown', '-R',
+                              '%s:%s' % (storage_id, storage_id),
+                              configdrive_dir, run_as_root=True)
             finally:
                 if mounted:
                     utils.execute('umount', tmpdir, run_as_root=True)