Fix image sprawl miscalculation

Signed-off-by: Thomas Sjögren <konstruktoid@users.noreply.github.com>

tests/6_docker_security_operations.sh

@@ -20,7 +20,7 @@ check_6_1() {
   images=$(docker images -q | sort -u | wc -l | awk '{print $1}')
   active_images=0
 
-  for c in $(docker inspect --format "{{.Image}}" "$(docker ps -qa)" 2>/dev/null); do
+  for c in $(docker inspect --format "{{.Image}}" $(docker ps -qa) 2>/dev/null); do
     if docker images --no-trunc -a | grep "$c" > /dev/null ; then
       active_images=$(( active_images += 1 ))
     fi