When using externally managed certificates, according to [1],
one should set `kolla_externally_managed_cert: yes` and ensure
that the certificates are in the correct place.

However, RabbitMQ precheck still expects the certificates to be
available on the controller node. This is incorrect.

Fix by not running the tasks in question when `kolla_externally_managed_cert: yes`

[1] https://docs.openstack.org/kolla-ansible/latest/admin/tls.html



Closes-Bug: 1999081
Related-Bug: 1940286
Signed-off-by: Magnus Lööf <magnus.loof@basalt.se>
Change-Id: I9f845a7bdf5055165e199ab1887ed3ccbfb9d808