Fix output of wwctl container show

Commit d8cd6049 introduced erroneous output coming from an
inner function of container show, and (seemingly) erroneously
replaces valid kernel versions with "not found". This commit
fixes both of those issues, and moves the output to the outer
cli function.

internal/app/wwctl/container/show/main.go

@@ -25,6 +25,7 @@ func CobraRunE(cmd *cobra.Command, args []string) (err error) {
 		fmt.Printf("%s\n", r.Rootfs)
 	} else {
 		fmt.Printf("Name: %s\n", r.Name)
+		fmt.Printf("KernelVersion: %s\n", r.KernelVersion)
 		fmt.Printf("Rootfs: %s\n", r.Rootfs)
 		fmt.Printf("Nr nodes: %d\n", len(r.Nodes))
 		fmt.Printf("Nodes: %s\n", r.Nodes)