Simplify fx infra (#485)

* add --host and --kubeconf to `fx up`
* remove `fx infra list` and `fx infra use`
* put assets into skip dir for golangci

* fix lint issue

* upgrade go-ssh-client to consume the 'Connectable' API, enable more
friendly SSH connection error message

* parse 'host' and 'kubeconf' for `fx list` and `fx down` also

* refactor parse

* clean infra stuff

context/context.go

@@ -52,6 +52,7 @@ func (ctx *Context) GetCliContext() *cli.Context {
 
 // Set a value with name
 func (ctx *Context) Set(name string, value interface{}) {
+	// nolint
 	newCtx := context.WithValue(ctx.Context, name, value)
 	ctx.Context = newCtx
 }