Make k8s_drain work when only one pod is present (#770)

SUMMARY
Fixes #769 .
k8s_drain was not checking if a pod has been deleted when there was only one pod on the node to be drained.
The list of pods, pods, was being "popped" before the first iteration of the while loop:
        pod = pods.pop()
        while (_elapsed_time() < wait_timeout or wait_timeout == 0) and pods:
When pods contains only one element, the while loop is skipped.


ISSUE TYPE


Bugfix Pull Request

COMPONENT NAME

k8s_drain

Reviewed-by: Mike Graves <mgraves@redhat.com>

changelogs/fragments/770-fix-k8s-drain-doesnt-wait-for-single-pod.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - k8s_drain - Fix k8s_drain does not wait for single pod (https://github.com/ansible-collections/kubernetes.core/issues/769).

plugins/modules/k8s_drain.py

@@ -291,16 +291,17 @@ class K8sDrainAnsible(object):
             return (datetime.now() - start).seconds
 
         response = None
-        pod = pods.pop()
+        pod = None
         while (_elapsed_time() < wait_timeout or wait_timeout == 0) and pods:
             if not pod:
-                pod = pods.pop()
+                pod = pods[-1]
             try:
                 response = self._api_instance.read_namespaced_pod(
                     namespace=pod[0], name=pod[1]
                 )
                 if not response:
                     pod = None
+                    del pods[-1]
                 time.sleep(wait_sleep)
             except ApiException as exc:
                 if exc.reason != "Not Found":
@@ -308,6 +309,7 @@ class K8sDrainAnsible(object):
                         msg="Exception raised: {0}".format(exc.reason)
                     )
                 pod = None
+                del pods[-1]
             except Exception as e:
                 self._module.fail_json(msg="Exception raised: {0}".format(to_native(e)))
         if not pods: