Allow BES uploads to complete before shutting down VMs

https://bazel.build/reference/command-line-reference#flag--bes_upload_mode
Signed-off-by: Alex Alvarez <[email protected]>

Author: alexander-alvarez

.bazelrc

@@ -136,7 +136,7 @@ build:remote-ci-common --remote_executor=grpcs://envoy.cluster.engflow.com
 build:remote-ci-common --bes_backend=grpcs://envoy.cluster.engflow.com/
 build:remote-ci-common --bes_results_url=https://envoy.cluster.engflow.com/invocation/
 build:remote-ci-common --bes_lifecycle_events
-build:remote-ci-common --bes_upload_mode=fully_async
+build:remote-ci-common --bes_upload_mode=wait_for_upload_complete
 build:remote-ci-common --jobs=40
 build:remote-ci-common --verbose_failures
 build:remote-ci-common --spawn_strategy=remote,sandboxed,local