Fix RabbitMQ hostname address resolution precheck

Make it require uniqueness of resolution as well to avoid later
issues with RabbitMQ going crazy.

Change-Id: I000ba6c62ab44eac0abdf8d5d1f069adfbc6552f
Closes-bug: #1863363

ansible/roles/rabbitmq/tasks/precheck.yml

@@ -59,12 +59,14 @@
   register: rabbitmq_hostnames
   with_items: "{{ groups['rabbitmq'] }}"
 
-- name: Check if rabbit hostname resolves to IP address of api_interface
+- name: Check if each rabbit hostname resolves uniquely to the proper IP address
   fail:
-    msg: "Hostname has to resolve to IP address of api_interface"
-  with_items: "{{ rabbitmq_hostnames.results }}"
+    msg: Hostname has to resolve uniquely to the IP address of api_interface
+  with_subelements:
+    - "{{ rabbitmq_hostnames.results }}"
+    - stdout_lines
   when:
-    - "item.stdout.find('api' | kolla_address(item['item'])) == -1"
+    - not item.1 is match('^'+('api' | kolla_address(item.0.item))+'\\b')
 
 - name: Checking free port for outward RabbitMQ
   wait_for:
@@ -120,10 +122,12 @@
   when:
     - enable_outward_rabbitmq | bool
 
-- name: Check if rabbit hostname resolves to IP address of api_interface
+- name: Check if each rabbit hostname resolves uniquely to the proper IP address
   fail:
-    msg: "Hostname has to resolve to IP address of api_interface"
-  with_items: "{{ outward_rabbitmq_hostnames.results }}"
+    msg: Hostname has to resolve uniquely to the IP address of api_interface
+  with_subelements:
+    - "{{ outward_rabbitmq_hostnames.results }}"
+    - stdout_lines
   when:
     - enable_outward_rabbitmq | bool
-    - "item.stdout.find('api' | kolla_address(item['item'])) == -1"
+    - not item.1 is match('^'+('api' | kolla_address(item.0.item))+'\\b')

releasenotes/notes/bug-1863363-eb5d0ddd0d0d1090.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Makes RabbitMQ hostname address resolution precheck stronger by
+    requiring uniqueness of resolution to avoid later issues.
+    `LP#1863363 <https://launchpad.net/bugs/1863363>`