Modify PCSContainerInstance to use keyword arguments (#1421)

Summary:
Pull Request resolved: #1421

X-link: facebookresearch/fbpcp#400

## Context
We want to enable customized containers in our infra ([design doc](https://docs.google.com/document/d/1UqaK6VXEoIVUHSJnYs_Ydju8)). Therefore we need to add cpu & memory properties to ContainerInstance;
## This commit
Change ```PCSContainerInstance``` to use keyword arguments to prevent breaks when we add cpu and memory to ```ContainerInstance ``` later

Reviewed By: joe1234wu

Differential Revision: D38553232

fbshipit-source-id: b0a004a5435e08737ac9e86243bb06b9dfbb9a27

fbpcs/common/entity/pcs_container_instance.py

@@ -23,8 +23,8 @@ def from_container_instance(
         cls, container_instance: ContainerInstance, log_url: Optional[str] = None
     ) -> "PCSContainerInstance":
         return cls(
-            container_instance.instance_id,
-            container_instance.ip_address,
-            container_instance.status,
-            log_url,
+            instance_id=container_instance.instance_id,
+            ip_address=container_instance.ip_address,
+            status=container_instance.status,
+            log_url=log_url,
         )