Do not silence errors during manifest inspection

Log the reason docker manifest inspect failed to help debugging.
It may fail in an unexpected way, eg. if dockerhub is rate limiting us.

Signed-off-by: Bence Szépkúti <[email protected]>

Author: bensze01

vars/gen_jobs.groovy

@@ -724,7 +724,7 @@ def gen_dockerfile_builder_job(String platform, boolean overwrite=false) {
     def cache = "$image-cache-$arch"
     def check_docker_image
     if (common.is_open_ci_env) {
-        check_docker_image = "docker manifest inspect $common.docker_repo:$tag > /dev/null 2>&1"
+        check_docker_image = "docker manifest inspect $common.docker_repo:$tag >/dev/null"
     } else {
         check_docker_image = "aws ecr describe-images --region eu-west-1 --repository-name $common.docker_repo --image-ids imageTag=$tag"
     }