Fix failing test due to missing param

Author: toote

tests/command.bats

@@ -217,7 +217,7 @@ expected_container_definition='[\n  {\n    "essential": true,\n    "image": "hel
   export BUILDKITE_PLUGIN_ECS_DEPLOY_EXECUTION_ROLE=arn:aws:iam::012345678910:role/world
 
   stub aws \
-    "ecs register-task-definition --family hello-world --container-definitions $'$expected_container_definition' : echo '{\"taskDefinition\":{\"revision\":1}}'" \
+    "ecs register-task-definition --family hello-world --container-definitions $'$expected_container_definition' --execution-role-arn arn:aws:iam::012345678910:role/world : echo '{\"taskDefinition\":{\"revision\":1}}'" \
     "ecs describe-services --cluster my-cluster --service my-service --query 'services[?status==\`ACTIVE\`].status' --output text : echo '1'" \
     "ecs describe-services --cluster my-cluster --services my-service --query 'services[?status==\`ACTIVE\`]' : echo 'null'" \
     "ecs update-service --cluster my-cluster --service my-service --task-definition hello-world:1 : echo ok" \