vnet: update help message for intfc state

Add useful help information on set interface state.

Change-Id: Ibcdcea2849ccaee4cc72bf38d79102beb0d4be11
Signed-off-by: Ray Kinsella <ray.kinsella@intel.com>
diff --git a/src/vnet/interface_cli.c b/src/vnet/interface_cli.c
index b17072a..94eb7ea 100644
--- a/src/vnet/interface_cli.c
+++ b/src/vnet/interface_cli.c
@@ -829,7 +829,7 @@
  ?*/
 VLIB_CLI_COMMAND (set_state_command, static) = {
   .path = "set interface state",
-  .short_help = "Set interface state",
+  .short_help = "set interface state <if-name> [up|down|punt|enable]",
   .function = set_state,
 };
 /* *INDENT-ON* */