Cap ansible.posix below 1.6.0

Collection ansible.posix 1.6.0 was released [1] which drops support for
ansible-core 2.14 [2]: ansible-core 2.15 is the minimum required version
for this release.

We need to use an earlier release to match the minimum Ansible version
in kolla-ansible.

[1] https://github.com/ansible-collections/ansible.posix/blob/1.6.0/CHANGELOG.rst#major-changes
[2] ansible-collections/ansible.posix#562

Change-Id: I3aed6c8ff61938301c7265f78fa7a57815e81c81
Closes-Bug: #2080609
(cherry picked from commit c1cbbd0)

Author: priteau

docker/kolla-toolbox/requirements.yml

@@ -1,7 +1,7 @@
 ---
 collections:
   - name: ansible.posix
-    version: '<2'
+    version: '<1.6.0'
   - name: community.general
     version: '<4'
   - name: community.mysql

releasenotes/notes/bug-2080609-51f216ad1ba47d20.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes incompatibility between ``ansible.posix`` 1.6.0 and ``ansible-core``
+    versions below 2.15 by capping ``ansible.posix`` to 1.5.x.
+    `LP#2080609 <https://launchpad.net/bugs/2080609>`__