The variable {{ node_config_directory }} is used for the configuration
directory on the remote hosts, and should not be used for paths on the
deploy host (localhost).

This changes the default value of the TLS certificate and CA file to
reference {{ CONFIG_DIR }}, in line with the directory used for
admin-openrc.sh (as of I0709482ead4b7a67e82796e17f85bde151e71bc0).

This change also introduces a variable, {{ node_config }}, that
references {{ CONFIG_DIR | default('/etc/kolla') }}, to remove
duplication.

Change-Id: Ibd82ac78630ebfff5824c329d7399e1e900c0ee0
Closes-Bug: #1804025