Don't use become for Kolla Ansible

Using become for all Kolla Ansible tasks is not ideal from a security
perspective. It is also incompatible with fact caching, since it causes
facts to be gathered and cached as root, which changes some facts.

This change modifies the default value of kolla_ansible_become to false.

Change-Id: I9ee5c55e59276f70c92e9c698c01123dcf8919a1
Story: 2007492
Task: 39217