Add cache plugin to coredns

[Bolodya1997]

Adds cache plugin to coredns.

[edwarnicke]

I like DNS caching a lot... but am curious what triggered adding this :)

[Bolodya1997]

I like DNS caching a lot... but am curious what triggered adding this :)

Looks like ping have some timeout to make DNS resolving - tried locally with setting 10ms latency between kind nodes and it always fails. And it looks like sometimes it is a problem when we testing it on the real clouds.
So we can start using nslookup instead of ping in our tests, but it probably wouldn't look so good. The other solution we can try is to add cache plugin to fix issue with latency between the Client and the Endpoint nodes.

[denis-tingaikin]

@edwarnicke Yes, I suggested to use the cache to avoid some unexpected issues that @Bolodya1997 found(#38 (comment)) during testing failed build on CI. As side effect it could a bit improve performance for DNS NSM scenarios :)

[denis-tingaikin]

@edwarnicke Do you have any additional comments on this PR?

[edwarnicke]

I am a huge fan of the cache... thank you for explaining what was going on :)