multitenant/tenantcostclient: TestConsumptionExternalStorage failed

multitenant/tenantcostclient.TestConsumptionExternalStorage [failed](https://mesolite.cluster.engflow.com/invocations/default/82ee2053-dfc3-4d7b-a908-5a90227600fe?testReportRun=2&testReportShard=1&testReportAttempt=1#targets-Ly9wa2cvbXVsdGl0ZW5hbnQvdGVuYW50Y29zdGNsaWVudDp0ZW5hbnRjb3N0Y2xpZW50X3Rlc3Q=) on master @ [3a1ac8769b237029f9600bddabb10dd79fbe372d](https://github.com/cockroachdb/cockroach/commits/3a1ac8769b237029f9600bddabb10dd79fbe372d):

```
=== RUN TestConsumptionExternalStorage
test_log_scope.go:172: test logs captured to: outputs.zip/logTestConsumptionExternalStorage1501087419
test_log_scope.go:82: use -show-logs to present logs inline
=== RUN TestConsumptionExternalStorage/backup_from_tenant_increments_egress_bytes
```

Parameters:
- attempt=1
- race=true
- run=2
- shard=1
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

/cc @cockroachlabs/server

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*TestConsumptionExternalStorage.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Jira issue: CRDB-65983

Start with multitenant/tenantcostclient.TestConsumptionExternalStorage and inspect the captured test logs at outputs.zip/logTestConsumptionExternalStorage1501087419. Reproduce the race-enabled failure using the reported test parameters, determine why backup_from_tenant_increments_egress_bytes fails, and confirm that the test passes without introducing regressions.

Written by the indexing model from the issue text.