Initial support for mdadm RAID arrays

This patch adds initial support for handling MD RAID arrays.  Adding
a pass at the very end of the shutdown sequence to signal any external
RAID controller to clear its state before we proceed to halt/reboot.

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

helpers.h

@@ -28,6 +28,7 @@
 #include <stdio.h>
 #include <string.h>		/* strerror() */
 #include <syslog.h>
+#include <sys/types.h>
 
 #define DO_LOG(level, fmt, args...)				\
 do {								\