[Core][RunPod] Fix list instances in RunPod Provisioner (#3878)

* fix

* simplify

* Revert "simplify"

This reverts commit 1057b90.

sky/provision/runpod/utils.py

@@ -77,7 +77,11 @@ def list_instances() -> Dict[str, Dict[str, Any]]:
         info['name'] = instance['name']
         info['port2endpoint'] = {}
 
-        if instance['desiredStatus'] == 'RUNNING' and instance.get('runtime'):
+        # Sometimes when the cluster is in the process of being created,
+        # the `port` field in the runtime is None and we need to check for it.
+        if (instance['desiredStatus'] == 'RUNNING' and
+                instance.get('runtime') and
+                instance.get('runtime').get('ports')):
             for port in instance['runtime']['ports']:
                 if port['isIpPublic']:
                     if port['privatePort'] == 22: