Previously, each provider's package-level 'New' function was being
called.
That made mocking it out for a different function that records data or
returns different output quite difficult.
This PR introduces an additional layer of abstraction in the form of
effectively a vtable struct for the dns providers. It's defaulted to the
same package-level constructors as before, but unit tests in the dns
package can easily override it.
A new test for the previously-introduced route53 trimming behavior is
also added.
If /etc/resolv.conf does not have any entries, then its unlikely
that the domain name representation of google's DNS would get
resolved too. Hence using IP address directly makes sense.
Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Log potential errors while waiting for DNS record propagation
**What this PR does / why we need it**:
This helps debugging, e.g. if there are network problems.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
```
