Chronos tasks w/o docker

[nz87]

We use the $MESOS_SANDBOX variable where cloudpickle should reside but when we run our stuff cloudpickle can not be found. The variable and it's content should be checked.

[nz87]

After some investigation we noticed that chronos uses it's task/job id as directory name which contains colons and that directory is in $MESOS_SANDBOX which we'd liked to add to $PYTHONPATH but it will be cut by colons even if they're escaped. On the other hand inside a docker container $MESOS_SANDBOX is /mnt/mesos/sandbox: no colons = no problems.