New option to trigger paunch configuration on only one container.

Adding the container_name option enables one to create playbook like
this:

    - hosts: Compute
      gather_facts: true
      become: true
      tasks:
        - name: update one container
          paunch:
            config: "/var/lib/tripleo-config/container-startup-config/step_4"
            config_id:
             - 'tripleo_step4'
            container_name: ovn_controller
            action: apply
            container_cli: podman
            managed_by: tripleo-Compute
            config_overrides:
              image: undercloud-0.ctlplane.redhat.local:8787/openstack-ovn-controller:16.1_20201020.1_hotfix
            cleanup: True

In this example we deliver an specific change to all Compute node
without running the entire update process.

This is only syntaxic sugar as running with:

    config: "/var/lib/tripleo-config/container-startup-config/step_4/hashed-ovn_controller.json"

has the same effect.

Note that config_overrides doesn't have the same semantic when we use
the container_name option as we don't require the user to pass the
full structure where it should be (still in the context of offering
some more convenience to the user):

   { <container_name>: {<changed_key>: <change>, ...} }

Here we prepend the container_name to the structure so that the user
focus on the container parameter.

This file has been deleted after ussuri so this patch starts at
ussuri.

Change-Id: I70ccfad3ea96dff44641bf70d459adb7cccb21d5

tripleo_ansible/ansible_plugins/modules/paunch.py

@@ -106,6 +106,11 @@ options:
       - Whether or not we cleanup containers not in config. Useful only for apply action.
     type: bool
     default: True
+  container_name:
+    description:
+      - If given just run paunch for the specified container.
+    default: ""
+
 """
 
 EXAMPLES = """
@@ -161,6 +166,14 @@ class PaunchManager:
         self.container_cli = self.module.params['container_cli']
         self.cleanup = self.module.params['cleanup']
         self.config_overrides = self.module.params['config_overrides']
+        self.container_name = None
+        if self.module.params['container_name']:
+            self.container_name = self.module.params['container_name']
+            # we simplify the user interface here, as if he/she wants
+            # override and give a name then it must be for that container.
+            self.config_overrides = {
+                self.container_name: self.module.params['config_overrides']
+            }
         self.container_log_stdout_path = \
             self.module.params['container_log_stdout_path']
         self.managed_by = self.module.params['managed_by']
@@ -184,8 +197,12 @@ class PaunchManager:
             if self.config.endswith('.json'):
                 self.module.warn('Only one config was given, cleanup disabled')
                 self.cleanup = False
+            container_name = None
+            if self.module.params['container_name']:
+                container_name = self.module.params['container_name']
             self.config_yaml = putils_common.load_config(
                 self.config,
+                name=container_name,
                 overrides=self.config_overrides)
 
         if self.action == 'apply':