capi: do not exit if controller fails to extract.

Doing `logrus.Fatal` when a controller fails to be extracted means that
we abort the installer process without giving it a chance to stop the
capi-related processes that are still running.

Let's just return an error instead and let the Installer go through the
normal capi shutdown procedure.

Author: r4f4

pkg/clusterapi/system.go

@@ -463,7 +463,7 @@ func (c *system) runController(ctx context.Context, ct *controller) error {
 	// If the provider is not empty, we extract it to the binaries directory.
 	if ct.Provider != nil {
 		if err := ct.Provider.Extract(c.lcp.BinDir); err != nil {
-			logrus.Fatal(err)
+			return fmt.Errorf("failed to extract provider %q: %w", ct.Name, err)
 		}
 	}