Makes the release grab the actual latest version (istio#15449)

release/downloadIstioCandidate.sh

@@ -22,8 +22,9 @@ else
 fi
 
 if [ "x${ISTIO_VERSION}" = "x" ] ; then
-  ISTIO_VERSION=$(curl -L -s https://api.github.com/repos/istio/istio/releases/latest | \
-                  grep tag_name | sed "s/ *\"tag_name\": *\"\\(.*\\)\",*/\\1/")
+  ISTIO_VERSION=$(curl -L -s https://api.github.com/repos/istio/istio/releases | \
+                  grep tag_name | sed "s/ *\"tag_name\": *\"\\(.*\\)\",*/\\1/" | \
+                  sort -t"." -k 1,1 -k 2,2 -k 3,3 -k 4,4 | tail -n 1)
 fi
 
 if [ "x${ISTIO_VERSION}" = "x" ] ; then
@@ -51,4 +52,4 @@ printf "\n"
 printf "Begin the Istio pre-installation verification check by running:\n"
 printf "\t istioctl verify-install \n"
 printf "\n"
-printf "Need more information? Visit https://istio.io/docs/setup/kubernetes/install/ \n"
+printf "Need more information? Visit https://istio.io/docs/setup/kubernetes/install/ \n"