Migrated ephemeral_disk data does not retain ownership/permissions

[blalor]

Nomad version

Nomad v0.5.0

Operating system and Environment details

CentOS 7.2

Issue

When the allocation directory is migrated from one nomad client to another, permissions on the files are not retained. Files are unarchived as root (as that's what Nomad's running as in my environment).

Reproduction steps

Use jobspec below; set the constraint so that the job runs to completion on one host, then run it again with the constraint updated so that it runs on another node. The 2nd placement will fail because the permissions are wrong on the files that were transferred from the other node.

Job file

job "migration-test" {
    region = "ci_aws_gen_us-east-1"
    
    datacenters = [
        "us-east-1d",
    ]
    
    type = "batch"
    
    constraint {
        attribute = "${attr.unique.hostname}"
        value     = "nomad-client-01425692"
    }

    group "grp" {
        ephemeral_disk {
            sticky = true
            migrate = true
            size = 101
        }

        task "test" {
            driver = "exec"

            config {
                command = "/bin/bash"
                
                args = [
                    "-c", "ls -al ${NOMAD_ALLOC_DIR}/data; (echo \"==> ${NOMAD_ALLOC_ID}\"; env) >> ${NOMAD_ALLOC_DIR}/data/test.out"
                ]
            }
        }
    }
}

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