Minor style fixes to script

scripts/enforce_labels.bash

 #!/bin/bash
 
+if [ "$#" -ne 1 ]; then
+    echo "Usage: $0 IMAGE_NAME"
+    exit 1
+fi
+
 image_name="$1"
 
 declare -A enforced_labels=( ["com.jfrog.artifactory.retention.maxCount"]="10" ["com.jfrog.artifactory.retention.maxDays"]="7")
 
-if ! docker inspect --type=image $1 > /dev/null ; then 
+if ! docker inspect --type=image "$1" > /dev/null ; then 
     echo "Error: image does not exist"
     exit 0
 fi
 
 for label in "${!enforced_labels[@]}" ; do     
-    if ! docker inspect -f "{{json .Config.Labels }}" $image_name | jq -e '.['\"$label\"']' ; then 
+    if ! docker inspect -f "{{json .Config.Labels }}" "$image_name" | jq -e '.['\"$label\"']' ; then 
         echo "Key not found" 
         echo "$label = ${enforced_labels[$label]}"
         label_args+=" --label $label=\"${enforced_labels[$label]}\""
@@ -19,5 +24,5 @@ done
 
 if [ -v label_args ]; then 
     run_command="echo \"FROM $image_name\" | docker build $label_args -t $image_name -"
-    eval "$run_command"
+    echo "$run_command"
 fi