Fix credential_input_source to handle state: absent when target credential is missing
The credential_input_source module would error when trying to delete a
credential input source (state: absent) if the target credential didn't
exist. This breaks idempotent playbook runs where cleanup tasks assume
resources may already be gone.
The fix only applies to state: absent; state: present still correctly
fails when the target credential doesn't exist.
Co-authored-by: Liam Allen <lallen@redhat.com>
