Change DNS test to use dig instead of ping

The ping test would fail if icmp requests were blocked by the host, even
if dns was working correctly. Using dig ensures we don't try to talk to
he resolved host at all.

Also restores the host tested to the one used before the workaround to
the related bug.

Related-Bug: #1968615
Change-Id: I121f49edb0ee8fedc085e6c6fc94f548b95c8713

roles/ipa-multinode/tasks/ipaserver-subnode-install.yml

@@ -165,15 +165,13 @@
       - "user: {{ freeipa_principal }}"
       - "password: {{ freeipa_admin_password }}"
 
-# Note(rlandy): Switching to IBM DNS
-# https://bugs.launchpad.net/tripleo/+bug/1968615 is fixed
 - name: Check DNS works
   shell: >
-    ping -c 5 ibm.com
-  register: ping_output_com
+    dig +tries=5 +timeout=5 redhat.com
+  register: dig_output_com
 
 - debug:
-    msg: "{{ ping_output_com.stdout }}"
+    msg: "{{ dig_output_com.stdout }}"
 
 - name: Check curl works with DNS
   shell: >

roles/ipa-multinode/tasks/ipaserver-undercloud-setup.yml

@@ -278,11 +278,9 @@
         state: present
       when: mirror_host_record_public.stdout_lines|length >=2
 
-# Note(rlandy): Switching to IBM DNS till
-# https://bugs.launchpad.net/tripleo/+bug/1968615 is fixed
 - name: Check that the DNS works
   shell: >
-    ping -c 10 ibm.com
+    dig +tries=5 +timeout=5 redhat.com
   register: dig_ouput_com
   ignore_errors: true