Make it clearer at time of install, that Kubernetes cluster must be able to talk to PMM server directly

[shoffman-percona]

I setup monitoring in my instance of Everest and used an IP that was internal to my network (which is also where everest is instlled). The installer accepted this and was able to provision an API user without issue. I noticed that no node was registered but assumed it wouldn't appear until I created a cluster. I was later able to choose this monitoring endpoint when i built my cluster but upon completion, still no node or service showed up.

I confirmed in the logs of the VM pod that it was also trying to access the private IP address for monitoring. I'm not sure the fix...maybe this isn't wildly common but need some sort of warning that your PMM server must be publicly accessible by IP (not hostname) from the K8s cluster. As soon as I saw the error I remember this limitation from PMM DBaaS but it was better spelled out as part of the setup.

couldn't send a block with size 221634 bytes to "1:secret-url": Post "http://192.168.0.2:8080/victoriametrics/api/v1/write": dial tcp4 192.168.0.2:8080: i/o timeout; re-sending the block in 60.000 seconds