dev-infrastructure/script/istio.sh: Download istioctl, tag the revisi…

…on tag with the target version, iterate through pods and do the istio version maintainance.

Created the istio.sh and run the shellscript after svc infra deployment pipeline. The shell script would make sure the istio service mesh in the cluster is in the right version.
This commit added the istio shell script and merge the istio maintances as part of the svc deployment.

dev-infrastructure/scripts/istio.sh

@@ -53,10 +53,6 @@ cd istio-"${ISTIOCTL_VERSION}"
 export PATH=$PWD/bin:$PATH
 echo "=========================================================================="
 
-#
-# Create the tag if it does not exist yet
-#
-
 ISTIO_NAMESPACE="aks-istio-system"
 
 echo "********** ISTIO Upgrade **************"