Pass proxy properties via MC_IMAGE_HELPER_OPTS (#3601)

scripts/start-utils

@@ -538,4 +538,18 @@ function buildDownloadList() {
     result+="${repoUrl}/${version}/$c"
   done
   echo "$result"
-}
+}
+
+function firstArrayElement {
+  local -n a="$1"
+  if (( ${#a[@]} )); then
+    echo "${a[0]}"
+  fi
+}
+
+function shiftArray {
+  local -n a="$1"
+  if (( ${#a[@]} )); then
+    a=("${a[@]:1}")
+  fi
+}