Add option for retry_servfail (#3247)

* Add option for retry_servfail

cf. https://dnspython.readthedocs.io/en/latest/resolver-class.html#dns.resolver.Resolver.retry_servfail

Setting this option to `True` allows for the possibility of the lookup plugin to retry and thereby recover from potentially transient lookup failures, which would otherwise cause the task or play to bail with an unrecoverable exception.

* Create 3247-retry_servfail-for-dig

* documentation for `retry_servfail` option

* Rename 3247-retry_servfail-for-dig to 3247-retry_servfail-for-dig.yaml

* fix whitespace

* Update plugins/lookup/dig.py

Co-authored-by: Ajpantuso <ajpantuso@gmail.com>

* Update plugins/lookup/dig.py

Co-authored-by: Ajpantuso <ajpantuso@gmail.com>

* rm try/except block

Co-authored-by: Ajpantuso <ajpantuso@gmail.com>

changelogs/fragments/3247-retry_servfail-for-dig.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - dig lookup plugin - add ``retry_servfail`` option (https://github.com/ansible-collections/community.general/pull/3247).

plugins/lookup/dig.py

@@ -35,6 +35,11 @@
       flat:
         description: If 0 each record is returned as a dictionary, otherwise a string
         default: 1
+      retry_servfail:
+        description: Retry a nameserver if it returns SERVFAIL.
+        default: false
+        type: bool
+        version_added: 3.6.0
     notes:
       - ALL is not a record per-se, merely the listed fields are available for any record results you retrieve in the form of a dictionary.
       - While the 'dig' lookup plugin supports anything which dnspython supports out of the box, only a subset can be converted into a dictionary.
@@ -73,6 +78,10 @@
 - ansible.builtin.debug:
     msg: "XMPP service for gmail.com. is available at {{ item.target }} on port {{ item.port }}"
   with_items: "{{ lookup('community.general.dig', '_xmpp-server._tcp.gmail.com./SRV', 'flat=0', wantlist=True) }}"
+
+- name: Retry nameservers that return SERVFAIL
+  ansible.builtin.debug:
+    msg: "{{ lookup('community.general.dig', 'example.org./A', 'retry_servfail=True') }}"
 """
 
 RETURN = """
@@ -300,6 +309,8 @@ def run(self, terms, variables=None, **kwargs):
                         rdclass = dns.rdataclass.from_text(arg)
                     except Exception as e:
                         raise AnsibleError("dns lookup illegal CLASS: %s" % to_native(e))
+                elif opt == 'retry_servfail':
+                    myres.retry_servfail = bool(arg)
 
                 continue