kpod: shut down the storage library before exiting

Before exiting, have kpod shut down the storage library if it can.  This
should keep us from leaving mountpoints for the root (for non-vfs cases)
and run directory (with newer containers/storage) busy when testing kpod.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

cmd/kpod/main.go

@@ -50,6 +50,16 @@ func main() {
 		}
 		return nil
 	}
+	app.After = func(*cli.Context) error {
+		// called by Run() when the command handler succeeds
+		shutdownStores()
+		return nil
+	}
+	cli.OsExiter = func(code int) {
+		// called by Run() when the command fails, bypassing After()
+		shutdownStores()
+		os.Exit(code)
+	}
 	app.Flags = []cli.Flag{
 		cli.StringFlag{
 			Name:  "config, c",
@@ -82,6 +92,6 @@ func main() {
 	}
 	if err := app.Run(os.Args); err != nil {
 		logrus.Errorf(err.Error())
-		os.Exit(1)
+		cli.OsExiter(1)
 	}
 }