Fix EKS when only one zone/region is set

My previous refactor likely broke this code, at least when specifying a singular region via eg `--zones=us-west-1`, which resulted in `--node-zones=us-west-1` being passed to eks create command.

PiperOrigin-RevId: 751088507

Author: Zach Howell

perfkitbenchmarker/providers/aws/elastic_kubernetes_service.py

@@ -255,19 +255,21 @@ def _GetNodeFlags(
   ) -> Dict[str, Any]:
     """Get common flags for creating clusters and node_groups."""
     tags = util.MakeDefaultTags()
-    return {
+    node_flags = {
         'nodes': nodepool_config.num_nodes,
         'node-labels': f'pkb_nodepool={nodepool_config.name}',
         'node-type': nodepool_config.machine_type,
         'node-volume-size': nodepool_config.disk_size,
-        # zone may be split a comma separated list
-        'node-zones': nodepool_config.zone,
         'region': self.region,
         'tags': ','.join(f'{k}={v}' for k, v in tags.items()),
         'ssh-public-key': (
             aws_virtual_machine.AwsKeyFileManager.GetKeyNameForRun()
         ),
     }
+    if self.control_plane_zones:
+      # zone may be split a comma separated list or simply a region
+      node_flags['node-zones'] = nodepool_config.zone
+    return node_flags
 
   def _IsReady(self):
     """Returns True if the workers are ready, else False."""

tests/providers/aws/elastic_kubernetes_service_test.py

@@ -7,6 +7,7 @@
 from perfkitbenchmarker.providers.aws import aws_network
 from perfkitbenchmarker.providers.aws import elastic_kubernetes_service
 from perfkitbenchmarker.providers.aws import util
+from tests import matchers
 from tests import pkb_common_test_case
 
 
@@ -55,6 +56,29 @@ def setUp(self):
   def testInitEksClusterWorks(self):
     elastic_kubernetes_service.EksCluster(EKS_SPEC)
 
+  def testEksClusterCreateNoSpec(self):
+    issue_command = self.MockIssueCommand(
+        {'create cluster': [('Cluster created', '', 0)]}
+    )
+    spec = container_spec.ContainerClusterSpec(
+        'NAME',
+        **{
+            'cloud': 'AWS',
+            'vm_spec': {
+                'AWS': {'machine_type': 'm5.large', 'zone': 'us-east-1'}
+            },
+        },
+    )  # {}, flag_values=flags.FLAGS)  #
+    cluster = elastic_kubernetes_service.EksCluster(spec)
+    cluster._Create()
+    issue_command.func_to_mock.assert_has_calls([
+        mock.call(
+            matchers.NOT(['node-zones']),
+            timeout=1800,
+            raise_on_failure=False,
+        ),
+    ])
+
   def testEksClusterCreate(self):
     issue_command = self.MockIssueCommand(
         {'create cluster': [('Cluster created', '', 0)]}