Fix condition for `r.pollRefresh()`

[mlajkim]

Description

r.pollRefresh() must run only when the following condition all met:

• config.ProviderService == ""
• config.CertFile != ""
• config.KeyFile != ""

But current code only checks config.ProviderService == "", and it is a bug.

Reference:

• https://github.com/AthenZ/k8s-athenz-sia/blob/main/pkg/certificate/service.go#L188
• https://github.com/AthenZ/k8s-athenz-sia/blob/main/pkg/certificate/service.go#L199

Assignees

• [x] Assignees is set

Type of changes

• [x] Apply one or more labels of the following that fits:
  • bug: Bug fix
  • dependencies: Dependency upgrades
  • documentation: Documentation changes
  • enhancement: New Feature
  • good first issue: First contribution
  • logging: Log changes
  • refactor: Refactoring (no functional changes, no api changes)

Flags

- [ ] Breaks backward compatibility
- [ ] Requires a documentation update
- [ ] Has untestable code

---

Checklist

- [ ] Followed the guidelines in the CONTRIBUTING document
- [ ] Added prefix `[skip ci]`/`[ci skip]`/`[no ci]`/`[skip actions]`/`[actions skip]` in the PR title if necessary
- [ ] Tested and linted the code
- [ ] Commented the code
- [ ] Made corresponding changes to the documentation

Checklist for maintainer

- [ ] Use `Squash and merge`
- [ ] Double-confirm the merge message has prefix `[skip ci]`/`[ci skip]`/`[no ci]`/`[skip actions]`/`[actions skip]`
- [ ] Delete the branch after merge

[mlajkim]

Issue created for a potential refactor here: https://github.com/AthenZ/k8s-athenz-sia/issues/119