Simplify node, profile, and image completions

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/app/wwctl/power/on/root.go

@@ -19,7 +19,7 @@ func GetCommand() *cobra.Command {
 		Long:              "This command will power on a set of nodes specified by PATTERN.",
 		RunE:              CobraRunE(&vars),
 		Args:              cobra.MinimumNArgs(1),
-		ValidArgsFunction: completions.Nodes(0), // no limit,
+		ValidArgsFunction: completions.Nodes,
 	}
 	powerCmd.PersistentFlags().BoolVarP(&vars.Showcmd, "show", "s", false, "only show command which will be executed")
 	powerCmd.PersistentFlags().IntVar(&vars.Fanout, "fanout", 50, "how many command should be executed in parallel")