[BGP] copy /etc/hosts from the undercloud to the test_host

In case of BGP jobs, the test host is different from the undercloud and
it may need to resolve some host names that are defined within the
undercloud's /etc/hosts file

Change-Id: Ib2b6bfbeb498035dd4207bc8a316a2f42c7d3f90

infrared_plugin/roles/tobiko-ir-before-run/tasks/main.yaml

@@ -8,12 +8,42 @@
 
 - name: ensure auto ssh key exchange in test host
   block:
-      - name: Retrieve public key from private key
-        command: "ssh-keygen -y -f ~/.ssh/id_rsa"
-        register: test_host_pubkey_result
+    - name: Retrieve public key from private key
+      command: "ssh-keygen -y -f ~/.ssh/id_rsa"
+      register: test_host_pubkey_result
 
-      - name: insert the public key to the known test host
-        authorized_key:
-            user: "{{ ansible_ssh_user }}"
-            key: "{{ test_host_pubkey_result.stdout }}"
+    - name: insert the public key to the known test host
+      authorized_key:
+        user: "{{ ansible_ssh_user }}"
+        key: "{{ test_host_pubkey_result.stdout }}"
   ignore_errors: yes
+
+- name: copy /etc/hosts from the undercloud to the test_host
+  block:
+    - name: read /etc/hosts from the undercloud
+      become: true
+      slurp:
+        src: /etc/hosts
+      delegate_to: "{{ groups.undercloud|first }}"
+      register: hosts_file
+
+    - name: write /etc/hosts to the test_host
+      become: true
+      copy:
+        content: "{{ hosts_file.content | b64decode }}"
+        dest: /etc/hosts
+        force: true
+        owner: root
+        group: root
+        mode: '0644'
+
+    - name: ensure 127.0.0.1 is not in the test_host /etc/hosts file
+      become: yes
+      lineinfile:
+        path: /etc/hosts
+        regexp: '^127.0.0.1 .*undercloud'
+        state: absent
+  ignore_errors: yes
+  when:
+    - groups.get("undercloud")
+    - test_host not in groups.undercloud