test: fix container name sanitisation

Signed-off-by: Babak K. Shandiz <babakks@github.com>

script/pgp-key-rotation-test

@@ -647,6 +647,7 @@ docker_teardown() {
 docker_client_setup() {
   image="$1"
   container_name="repo-client-${image//:/-}"
+  container_name="${container_name//\//-}"
   if [ "$(docker ps -a -q -f "name=^$container_name\$")" ]; then
     read -p "Do you want to teardown the existing container and recreate it? (y/n): " choice
     if [[ "$choice" == "y" || "$choice" == "Y" ]]; then