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/common.go

@@ -10,6 +10,10 @@ import (
 	"github.com/urfave/cli"
 )
 
+var (
+	stores = make(map[storage.Store]struct{})
+)
+
 func getStore(c *libkpod.Config) (storage.Store, error) {
 	options := storage.DefaultStoreOptions
 	options.GraphRoot = c.Root
@@ -22,9 +26,18 @@ func getStore(c *libkpod.Config) (storage.Store, error) {
 		return nil, err
 	}
 	is.Transport.SetStore(store)
+	stores[store] = struct{}{}
 	return store, nil
 }
 
+func shutdownStores() {
+	for store := range stores {
+		if _, err := store.Shutdown(false); err != nil {
+			break
+		}
+	}
+}
+
 func getConfig(c *cli.Context) (*libkpod.Config, error) {
 	config := libkpod.DefaultConfig()
 	if c.GlobalIsSet("config") {