Make the 'init <CMD | RUNLEVEL>' commands synchronous.

When a user changes runlevel, or wants to reload the config, we want the
command to return only when the operation has completed.  For instance,
rolling in a new system configuration in runlevel 1 requires that we are
sure we've actually entered that runlevel before rolling it in.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

finit.h

@@ -76,6 +76,7 @@
 #define INIT_MAGIC		0x03091969
 #define INIT_CMD_RUNLVL		1
 #define INIT_CMD_DEBUG		2
+#define INIT_CMD_ACK		255
 
 struct init_request {
 	int	magic;		/* Magic number			*/