Automatic merge from submit-queue (batch tested with PRs 49992, 48861, 49267, 49356, 49886)

Set default vmodule flag in integration tests

Re-introduce a default glog vmodule flag to the integration test setup.
The default was removed in d08dfb92 because it was hard-coded and
prevented local override. This commit makes the default overridable.

```release-note
NONE
```

/cc @caesarxuchao