update-m1n1: simplify & rename for manual management

Signed-off-by: b-crumb <[email protected]>

Author: b-crumb

update-m1n1

@@ -5,7 +5,7 @@ set -e
 
 [ -e /etc/default/update-m1n1 ] && . /etc/default/update-m1n1
 
-[ $M1N1_MANAGED_MANUALLY == 1 ] && exit 0
+[ -n $M1N1_UPDATE_DISABLED ] && exit 0
 
 if [ -e "$(dirname "$0")"/functions.sh ]; then
     . "$(dirname "$0")"/functions.sh