Do not use results from previous series version

Summary:
Previously, we could see the following sequence of events:

```
<v1 sent>
email: v1 fail
<v2 sent>
email: v2 fail       <<<
email: v2 success
```

`<<<` indicates that kpd was looking at the results from v1
but reporting against v2. This is confusing and wrong.

Example: kernel-patches/bpf#7070

 {F1647837371}

## Root cause

kpd, for each series on patchwork, does a reconcile-then-reap action.

In our case, during reconcile, kpd would:

1. Grab a handle to the existing PR
2. Remove v1 labels and add v2 labels
3. Force push the PR

At the end of reconciliation, the handle to the PR would have stale metadata
saying the PR HEAD still pointed to v1 (despite v2 already being pushed).

This means that when kpd goes to reap the results, it would filter workflow
runs based on the v1 sha, see the jobs have completed, and then report
the stale result against v2.

Fix by syncing the handle's metadata after a force push.

Reviewed By: chantra

Differential Revision: D57741395

fbshipit-source-id: 2974327c247b8bfc4028e566ab14254a53c9b891

kernel_patches_daemon/branch_worker.py

@@ -869,6 +869,9 @@ async def apply_push_comment(
                 can_create=True,
             )
             self.repo_local.git.push("--force", "origin", branch_name)
+            # Metadata inside `pr` may be stale from the force push; refresh it
+            if pr:
+                pr.update()
             return pr
         # we don't have a branch, also means no PR, push first then create PR
         elif branch_name not in self.branches: