Don't try to save partition tables for /dev/mapper devices

Right now backupninja shows Warnings when it tries to save the partition tables of my lvm devices.

As it's usual to have them under /dev/mapper/ I think it's safe to avoid those devices when doing backup of the partition table.

handlers/sys.in

@@ -608,7 +608,7 @@ fi
 
 if [ "$partitions" == "yes" ]; then
    if [ "$dosfdisk" == "yes" ]; then
-      devices=`LC_ALL=C $LSBLK --output NAME,TYPE --list --paths 2>/dev/null | grep "disk$" | @AWK@ '{print $1}'`
+      devices=`LC_ALL=C $LSBLK --output NAME,TYPE --list --paths 2>/dev/null | grep "disk$" | @AWK@ '{print $1}' | grep -v '/dev/mapper/'`
       if [ "$devices" == "" ]; then
          warning "No harddisks found"
       fi