Hello,

We have a process that fetches a file from one repo then push to different repository.

        dir('docker') {
            docker.withRegistry(BASE_IMAGE_REGISTRY_URL,  BASE_IMAGE_REGISTRY_JENKINS,) {
                docker.withRegistry(LOCAL_REGISTRY_URL, LOCAL_REGISTRY_JENKINS,) {
                     stage("package/docker") {
                          sh([script: 'make'])
                     }
                 }
             }
        }

We have discovered that the docker.withRegistry create a new `DOCKER_CONFIG` for each docker.withRegistry and traced it to `org.jenkinsci.plugins.docker.commons.impl.RegistryKeyMaterialFactory`.

Per each materialize() there is unconditional call to `createSecretsDirectory()` which loses loses the credentials in previous block.

In this implementation only a single docker registry may be authenticated, while docker supports many.

Suggested implementation:

1. Do not create new secrets directory if already exist, it can be checked via the `DOCKER_CONFIG` variable. Maybe force first time creation within the entire instance to isolate jenkins from system.
2. Use docker logout instead of removing `DOCKER_CONFIG` to clean up the credentials.

If this is acceptable I may be able to provide a patch.

Thanks!