replace baremetal_nic with api_interface

- The baremetal_nic variable was used as part of
  kolla host playbook when generating the /etc/hosts file.
  Populating the /etc/hosts is done to ensure that rabbitmq
  can reach the other nodes in the rabbitmq cluster by hostname.
- Before this change the baremetal_nic variable was used to
  determin which interface to read when mapping the hostname to
  an ip address.
- This change removes baremetal_nic and uses api_interface
  instead as the hostname used by rabbitmq should always map to the
  api_interface ip.

TrivialFix
Closes-Bug: #1618381

Change-Id: I65fe3aad58ac34b001a1f4a38641addc9fa5a1d4

ansible/roles/baremetal/defaults/main.yml

@@ -1,6 +1,4 @@
 ---
-baremetal_nic: "{{ api_interface | default('em1') }}"
-
 docker_apt_url: "https://apt.dockerproject.org"
 docker_apt_key_id: F76221572C52609D
 

ansible/roles/baremetal/tasks/append_to_etc_hosts.yml

@@ -5,7 +5,7 @@
   delegate_to: "{{ control_node }}"
 
 - name: get real node ip
-  shell: ip -4 addr show "{{ hostvars[control_node]['baremetal_nic'] }}" | grep -oP "(?<=inet )[\d\.]+(?=/)"
+  shell: ip -4 addr show "{{ hostvars[control_node]['api_interface'] }}" | grep -oP "(?<=inet )[\d\.]+(?=/)"
   register: real_node_ip
   delegate_to: "{{ control_node }}"