Allow user to get version without a server

[jmckulk]

If you don't have a running server, the current version command will fail.

$ KUBECONFIG=blah ./bin/kubectl-pgo version
Client Version: v0.4.1
W0123 12:49:15.331122 1788689 loader.go:221] Config not found: blah
Error: Get "http://localhost:8080/apis/apiextensions.k8s.io/v1/customresourcedefinitions/postgresclusters.postgres-operator.crunchydata.com": dial tcp 127.0.0.1:8080: connect: connection refused
$ echo $?
1

With the change, you can pass the --client or --client=true flag to skip the server and postgrescluster version check

$ KUBECONFIG=blah ./bin/kubectl-pgo version --client
Client Version: v0.4.1
$ echo $?
0

[tjmoore4]

Looks good 👍
🤔 Would it be worthwhile to add a check in our KUTTL tests?

[tjmoore4]

⛏️ I'd prefer to have the Expected/Actual error output for troubleshooting.