Separate outputs of kolla_toolbox inner module

Inner modules called by the kolla_toolbox module were returning stdout
and stderr as a single output object. This could break JSON parsing if
any data was present in stderr, for example warnings such as:

    [WARNING]: Collection ansible.posix does not support Ansible version 2.14.17

Fix by using demux=True to separate the two streams. The stderr content
is logged as it could be useful for troubleshooting or catching
deprecation notices.

Change-Id: Iad0476d4511f28c837794352c9a3e2f47113d9a1
Closes-Bug: #2080544

ansible/library/kolla_toolbox.py

@@ -162,7 +162,9 @@ def use_docker(module):
                    "ANSIBLE_LOAD_CALLBACK_PLUGINS": "True"}
     job = client.exec_create(kolla_toolbox, command_line,
                              environment=environment, **kwargs)
-    json_output = client.exec_start(job)
+    json_output, error = client.exec_start(job, demux=True)
+    if error:
+        module.log(msg='Inner module stderr: %s' % error)
 
     try:
         output = json.loads(json_output)

releasenotes/notes/kolla-toolbox-demux-c5e8d27bc7214069.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes parsing of JSON output of inner modules called by ``kolla-toolbox``
+    when data was returned on standard error.
+    `LP#2080544 <https://launchpad.net/bugs/2080544>`__