The kubeadm dry run client reactor code is flawed as it assumes
all invoked "get" verb actions can be casted to GetAction.
Apparently that is not the case when Discovery().ServerVersion()
and other discovery calls are made. In such cases the action
type is the bare ActionImpl.
Catch if an action can be casted to ActionImpl and construct a
GetAction from it. GetActionImpl only suppersets ActionImpl with
a Name field (empty string in this case).
Add unit test for Discovery().ServerVersion().
