ldomctl usage is incomplete

[Kaashif Hymabaccus]

ldomctl leaves out a ton of commands from its usage, this caused me a
moment of confusion while using it. We could list all commands
programatically like vmctl, or just a one-line thing like smtpctl. As
it is, it's a bit confusing since it lists some but not all commands.

diff --git ldomctl.c ldomctl.c
index 7e6dcb708a4..bf00bfe6b6b 100644
--- ldomctl.c
+++ ldomctl.c
@@ -159,8 +159,7 @@ usage(void)
 {
        extern char *__progname;
 
-       fprintf(stderr, "usage: %s start|stop|panic domain\n", __progname);
-       fprintf(stderr, "       %s status [domain]\n", __progname);
+       fprintf(stderr, "usage: %s command [argument ...]\n", __progname);
        exit(EXIT_FAILURE);
 }