syncucer will only write witrh syncuser switch

uid/gid are not synced at container import but checked. An apropriate
message is printed, regarding users which are not present on host.
The `wwctl container syncuser` needs the `--write` switch to actually
write to the container.

The command `wwctl container syncuser` will always operate at the
container level, but as the 'generic` overlay reads in the container
passwd/group, following two steps will update the passwd/group on a
running cluster:
1. Add passwd/group to container
wwctl container syncuser --write CONTAINER
2. Synchronize overlay
wwctl overlay build -N

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

@@ -130,8 +130,8 @@ func CobraRunE(cmd *cobra.Command, args []string) error {
 		wwlog.Printf(wwlog.WARN, "Could not copy /etc/resolv.conf into container: %s\n", err)
 	}
 
-	err = container.SyncUids(name, !NoSyncUser)
-	if err != nil && !NoSyncUser {
+	err = container.SyncUids(name, !SyncUser)
+	if err != nil && !SyncUser {
 		wwlog.Printf(wwlog.ERROR, "Error in user sync, fix error and run 'syncuser' manually: %s\n", err)
 		os.Exit(1)
 	}

internal/app/wwctl/container/imprt/root.go

@@ -24,7 +24,7 @@ Imported containers are used to create bootable VNFS images.`,
 	SetUpdate  bool
 	SetBuild   bool
 	SetDefault bool
-	NoSyncUser bool
+	SyncUser   bool
 )
 
 func init() {
@@ -32,7 +32,7 @@ func init() {
 	baseCmd.PersistentFlags().BoolVarP(&SetUpdate, "update", "u", false, "Update and overwrite an existing container")
 	baseCmd.PersistentFlags().BoolVarP(&SetBuild, "build", "b", false, "Build container when after pulling")
 	baseCmd.PersistentFlags().BoolVar(&SetDefault, "setdefault", false, "Set this container for the default profile")
-	baseCmd.PersistentFlags().BoolVar(&NoSyncUser, "nosyncuser", false, "Don't synchronize uis/gods from host to container")
+	baseCmd.PersistentFlags().BoolVar(&SyncUser, "syncuser", false, "Synchronize uis/gods from host to container")
 }
 
 // GetRootCommand returns the root cobra.Command for the application.