Replace HOST_POWERED_DOWN with HOST_POWERED_OFF state in Palmetto

The HOST_POWERED_DOWN has been deprecated and replaced with HOST_POWERED_OFF.
Update the Palmetto config file with the updated state define.
diff --git a/bin/Palmetto.py b/bin/Palmetto.py
index ee95999..7172364 100755
--- a/bin/Palmetto.py
+++ b/bin/Palmetto.py
@@ -19,7 +19,7 @@
 	'HOST_POWERED_ON',
 	'HOST_BOOTING',
 	'HOST_BOOTED',
-	'HOST_POWERED_DOWN',
+	'HOST_POWERED_OFF',
 ]
 
 EXIT_STATE_DEPEND = {