Enabling docker universe.

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This merge request is automatically copied from !358 (merged) orginally made by @maikenp
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Add possibility to submit jobs that run in docker container in htcondor.

To test out:

0)

Install and enable dockerand condor, and add user submitting the ARC job to the docker-group

1)

Map docker user in arc.conf e.g. like this if you have called your docker user dockerroot and the docker group dockerroot

[authgroups:alloweddockerusers]
subject=<your-openssl-identity>

[mapping]
unixmap=dockerroot:dockerroot authgroup alloweddockerusers

2)

Create a runtime environment file called DOCKER and place it in /ENV/DOCKER.

#!/bin/bash
export DOCKER_UNIVERSE=docker
export DOCKER_IMAGE=$2

Enable it with

arcctl rte enable ENV/DOCKER

3)

Create a job description file e.g. like this:

&(executable=runhello.sh)
(jobname=hello_docker)
(runtimeenvironment="ENV/DOCKER" "debian")
(stdout=std.out)
(stderr=std.err)
(cpuTime="1 hours")
(memory="1")
(inputfiles=(""))
(outputfiles=("output.txt" "" ))

With some executable runhello.sh e.g. like so:

#!/bin/sh
echo "Hello! Am sleeping for 120 seconds" >> output.txt
sleep 120
exit 

4)

Submit the job with e.g. arcsub

5)

Check that the docker container is running for the job sudo docker ps