Fix 'The libvirt module is not importable' error

Upper constraints were updated [1] to allow libvirt-python 7.5.0. The
first Kayobe builds using this version worked fine, but later they
started failing with the error:

    The `libvirt` module is not importable. Check the requirements.

The main difference is that successful jobs were using the source
archive libvirt-python-7.5.0.tar.gz, while failing jobs were using the
wheel libvirt_python-7.5.0-cp36-cp36m-linux_x86_64.whl.

Install libvirt-python from source to avoid this issue.

Update the ansible-lint configuration to ignore errors coming from the
stackhpc.libvirt-vm role, fixing the tenks-tox-ansible-lint job.

[1] https://review.opendev.org/c/openstack/requirements/+/799347

Change-Id: I746d01ed355330c965b90657264d89a4ef7995d2

.ansible-lint

@@ -1,3 +1,6 @@
 skip_list:
   - '106'  # Role name {} does not match ``^[a-z][a-z0-9_]+$`` pattern'
 
+warn_list:
+  - experimental
+  - no-changed-when

ansible/roles/virtualbmc-daemon/tasks/main.yml

@@ -34,9 +34,13 @@
     # following error: Cannot uninstall 'PyYAML'. It is a distutils installed
     # project and thus we cannot accurately determine which files belong to it
     # which would lead to only a partial uninstall.
+    # NOTE(priteau): Use --no-binary to avoid installing libvirt-python from
+    # wheel. There is a problem with the 7.5.0 wheel resulting in the error:
+    # The `libvirt` module is not importable. Check the requirements.
     extra_args: >-
       -c {{ vbmcd_python_upper_constraints_url }}
       {% if not vbmcd_virtualenv_path %}--ignore-installed PyYAML{% endif %}
+      --no-binary libvirt-python
     virtualenv: "{{ vbmcd_virtualenv_path or omit }}"
   register: result
   until: result is success