quote output filename

Shouldn't be necessary for output from `mktemp`, but better play it
safe.

letsencrypt.sh

@@ -43,11 +43,11 @@ hex2bin() {
 _request() {
   temperr="$(mktemp)"
   if [ "${1}" = "head" ]; then
-    curl -sSf -I "${2}" 2>${temperr}
+    curl -sSf -I "${2}" 2>"${temperr}"
   elif [ "${1}" = "get" ]; then
-    curl -sSf "${2}" 2>${temperr}
+    curl -sSf "${2}" 2>"${temperr}"
   elif [ "${1}" = "post" ]; then
-    curl -sSf "${2}" -d "${3}" 2>${temperr}
+    curl -sSf "${2}" -d "${3}" 2>"${temperr}"
   fi
   if [ ! -z "$(<${temperr})" ]; then echo "  + ERROR: An error occured while sending ${1}-request to ${2} ($(<"${temperr}"))" >&2; exit 1; fi
   rm -f "${temperr}"