The value of DO_SYNC property should be "yes"

In order to reenable fsync() the DO_SYNC image property should be
defined like this:
DO_SYNC=yes

snf-image-helper/tasks/10FixPartitionTable.in

@@ -58,7 +58,8 @@ if [ "$table_type" == "gpt" ]; then
     "$SGDISK" --move-second-header "$SNF_IMAGE_DEV"
 elif [ "$table_type" != "msdos" ]; then
     log_error "Device: \'${SNF_IMAGE_DEV}' contains unsupported partition " \
-        "table type: \`$table_type'. Only msdos & gpt partitions are supported."
+              "table type: \`$table_type'. Only msdos & gpt partitions are" \
+              "supported."
 fi
 
 last_part=$(get_last_partition "$table")

snf-image-helper/tasks/20FilesystemResizeUnmounted.in

@@ -41,7 +41,7 @@ if [ -z "$SNF_IMAGE_RESIZE_PART" ]; then
     exit 0
 fi
 
-if [ -n "$SNF_IMAGE_PROPERTY_DO_SYNC" ]; then
+if [ "x$SNF_IMAGE_PROPERTY_DO_SYNC" = "xyes" ]; then
     unset EATMYDATA
 fi