Fix kubectl-mongodb download location and permissions required for Code Snippets (#575)

# Summary

Multi cluster code snippets require `kubectl-mongodb` plugin being
available in the PATH. Previous attempt
#565 failed, because
the file was not in the correct path (missing evg workdir) and didn't
have required permissions (they were lost during `shutil.copyfiles`
execution)

## Proof of Work

Passing prerelease code snippets tests ->
https://spruce.mongodb.com/version/690db4a65b72a10007e62a47

## Checklist

- [ ] Have you linked a jira ticket and/or is the ticket in the title?
- [ ] Have you checked whether your jira ticket required DOCSP changes?
- [ ] Have you added changelog file?
    - use `skip-changelog` label if not needed
- refer to [Changelog files and Release
Notes](https://github.com/mongodb/mongodb-kubernetes/blob/master/CONTRIBUTING.md#changelog-files-and-release-notes)
section in CONTRIBUTING.md for more details

Author: MaciejKaras

.evergreen-functions.yml

@@ -524,6 +524,8 @@ functions:
   download_multi_cluster_binary:
     - command: subprocess.exec
       params:
+        include_expansions_in_env:
+          - workdir
         working_dir: src/github.com/mongodb/mongodb-kubernetes
         binary: scripts/release/kubectl_mongodb/download_kubectl_plugin.sh
         env:
@@ -791,6 +793,8 @@ functions:
           - code_snippets_reset
           - task_name
           - MDB_BASH_DEBUG
+        add_to_path:
+          - ${workdir}/bin
         script: |
           ./scripts/code_snippets/tests/${task_name}
 

scripts/release/kubectl_mongodb/download_kubectl_plugin.py

@@ -41,12 +41,18 @@ def download_kubectl_plugin_from_s3(
         # change the file's permissions to make file executable
         os.chmod(local_path, 0o755)
 
+        logger.info(f"Successfully downloaded artifact to {local_path}")
+
         if copy_to_bin_path:
-            shutil.copyfile(local_path, KUBECTL_MONGODB_PLUGIN_BIN_PATH)
+            kubectl_mongodb_workdir_path = os.path.join(os.getenv("workdir", ""), KUBECTL_MONGODB_PLUGIN_BIN_PATH)
+            # copy content, stat-info (mode too), timestamps..
+            shutil.copy2(local_path, kubectl_mongodb_workdir_path)
+            # preserve owner and group
+            st = os.stat(local_path)
+            os.chown(kubectl_mongodb_workdir_path, st.st_uid, st.st_gid)
+
+            logger.info(f"Copied kubectl-mongodb plugin to {kubectl_mongodb_workdir_path} for tests usage")
 
-        logger.info(
-            f"Successfully downloaded artifact to {local_path}{f" and {KUBECTL_MONGODB_PLUGIN_BIN_PATH}" if copy_to_bin_path else ""}"
-        )
     except ClientError as e:
         if e.response["Error"]["Code"] == "404":
             raise Exception(f"Artifact not found at s3://{s3_bucket}/{s3_plugin_path}: {e}")