fix: race in delete user functionality (#13547)

- The race happens with a goroutine that refreshes IAM cache data from storage.
- It could lead to deleted users re-appearing as valid live credentials.
- This change also causes CI to run tests without a race flag (in addition to
running it with).

.github/workflows/go-lint.yml

@@ -45,4 +45,5 @@ jobs:
           curl -L -o nancy https://github.com/sonatype-nexus-community/nancy/releases/download/${nancy_version}/nancy-${nancy_version}-linux-amd64 && chmod +x nancy
           go list -deps -json ./... | jq -s 'unique_by(.Module.Path)|.[]|select(has("Module"))|.Module' | ./nancy sleuth
           make
+          make test
           make test-race