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 <[email protected]>
(cherry picked from commit 4c305e7)

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

@@ -303,10 +303,10 @@ def _elapsed_time():
             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]
@@ -315,13 +315,15 @@ def _elapsed_time():
                     "name"
                 ):
                     pod = None
+                    del pods[-1]
                 time.sleep(wait_sleep)
             except ApiException as exc:
                 if exc.reason != "Not Found":
                     self._module.fail_json(
                         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: