CLOUDP-332653: mutually exclusively return errors or reconcile results

[s-urbaniak]

Summary

With #2525 logs are now being spammed with this INFO statement:

 1 | AtlasDeployment:
 2 |   name: test
 3 |   namespace: flex
 4 | controller: AtlasDeployment
 5 | controllerGroup: atlas.mongodb.com
 6 | controllerKind: AtlasDeployment
 7 | level: INFO
 8 | msg: "Warning: Reconciler returned both a non-zero result and a non-nil error. The result will always be ignored if the error is non-nil and the non-nil error causes requeuing with exponential backoff. For more details, see: https://pkg.go.dev/sigs.k8s.io/controller-runtime/pkg/reconcile#Reconciler"
 9 | name: test
10 | namespace: flex
11 | reconcileID: 67857508-03af-4eac-a8b7-8f704112f8cb
12 | time: 2025-07-21T13:43:38.046+0200

This is because reconcile.Result is non empty if errors are returned.

This fixes it.

Proof of Work

All unit tests have been adapted.

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you checked for release_note changes?
• Have you signed our CLA?

Reminder (Please remove this when merging)

• Please try to Approve or Reject Changes the PR, keep PRs in review as short as possible
• Remember the following Communication Standards - use comment prefixes for clarity:
  • blocking: Must be addressed before approval.
  • follow-up: Can be addressed in a later PR or ticket.
  • q: Clarifying question.
  • nit: Non-blocking suggestions.
  • note: Side-note, non-actionable. Example: Praise
  • --> no prefix is considered a question