Update minimum rancher version in Istio charts

Due to changes in the UI of the Istio chart we need to add minimum
Rancher versions to ensure that the Istio chart will display its UI
elements correctly within Rancher.

charts/rancher-istio/1.4.3/questions.yaml

 labels:
   rancher.istio.v1.4.3: 1.4.3
-rancher_min_version: 2.3.0-rc1
+rancher_min_version: 2.3.4-rc1

scripts/update-istio-release

@@ -45,11 +45,14 @@ EOF
 done
 rm -r charts/rancher-istio/${1}/charts/istio-init
 
-# Add question.yaml
+# Add question.yaml, make need to update minimum rancher version
+RANCHER_MIN_VERSION="2.3.4-rc1"
+echo "Current rancher min version is set to $RANCHER_MIN_VERSION"
+
 cat > charts/rancher-istio/${1}/questions.yaml << EOF
 labels:
   rancher.istio.v${1}: ${1}
-rancher_min_version: 2.3.0-rc1
+rancher_min_version: $RANCHER_MIN_VERSION
 EOF
 
 # Replace the name of the chart