Skaffold should support configuration options for normal docker credentials

[robbert229]

Expected behavior

I should be able to use Skaffold to push to private docker registries.

Actual behavior

Authentication with normal private docker registries doesn't function. Skaffold doesn't provide the configuration hooks to allow me to configure kaniko to push to my private registry. I would like to be able to pass down docker credentials to the kaniko instance, but currently there is no option to do so.

There is a bit of conversation in here -> GoogleContainerTools/kaniko#129 about how providing credentials to kaniko works.

In #1421 I provide an example of what fixes my current issues.

[robbert229]

@garethjevans has a real pr for this in #1466

[dgageot]

Fixed with #1466