Support building an allow-list of providers (#527)

* Add providers subcommand to verify providers

Allows users to check what providers are available

* Fix version output to add new line

This command was totally broken until we moved around the call to
`initConfig()`, this just fixes the output now that it works.

* Flip boolean of provider include tags

All providers are still included by default and fix tags using the old
format.

cmd/root.go

@@ -90,6 +90,8 @@ var RootCmd = &cobra.Command{
 backend implementation allowing users to create kubernetes nodes without running the kubelet.
 This allows users to schedule kubernetes workloads on nodes that aren't running Kubernetes.`,
 	Run: func(cmd *cobra.Command, args []string) {
+		initConfig()
+
 		defer rootContextCancel()
 
 		vk := vkubelet.New(vkubelet.Config{
@@ -167,8 +169,6 @@ func init() {
 	log.L = logruslogger.FromLogrus(logrus.NewEntry(logrus.StandardLogger()))
 	trace.T = opencensus.Adapter{}
 
-	cobra.OnInitialize(initConfig)
-
 	// read default node name from environment variable.
 	// it can be overwritten by cli flags if specified.
 	defaultNodeName := os.Getenv("DEFAULT_NODE_NAME")