Fix release script tagging wrong image name (#1257)

hack/release.sh

@@ -90,9 +90,9 @@ push_all_envs() {
 
 push_env_builder_image() {
     local version=$1
-    envdir=$2
-    imgnamebase=$3
-    imgvariant=$4
+    local envdir=$2
+    local imgnamebase=$3
+    local imgvariant=$4
 
     if [ -z "$imgvariant" ]
     then
@@ -101,7 +101,7 @@ push_env_builder_image() {
     else
         # variant specified - append variant to image name and assume dockerfile
         # exists with same suffix (e.g. image node-env-debian built from Dockerfile-debian)
-        imgname="$imgname-$imgvariant"
+        imgname="$imgnamebase-$imgvariant"
     fi
     echo "Pushing $envdir -> $imgname:$version"