fix version parameter

acme-downloader.sh

@@ -158,7 +158,7 @@ while true; do
         CHECK='CHECK'
         ;;
     --version)
-        PROG_VERSION='PROG_VERSION'
+        PARAM_VERSION='PARAM_VERSION'
         ;;
     --)
         shift
@@ -169,7 +169,7 @@ while true; do
 done
 
 # print version buildtime and say goodbye
-if [[ -n $PROG_VERSION ]]; then
+if [[ -n $PARAM_VERSION ]]; then
     echo "$(basename $0) version $PROG_VERSION built on ${BUILD_TIME}"
     clean_up 0
 fi