get the log files into an accessible area

[Angus Salkeld]

A container's log files can be accessed from mesos *if* we place them in the right directory.

in kolla_mesos_start.py we need to automatically set the logfile in openstack configs, as follows:

# mesos passes this env into all containers
LOG_DIR = env('MESOS_SANDBOX', '/tmp')

logfile = os.path.join(LOG_DIR, '%s.log' % service_name)
then add "logfile" to the variables that get passed to jinja.

[Angus Salkeld (asalkeld)]

Then new "drop root" changes to kolla images make (what I initially had in mind) difficult.

the /mnt/mesos/sandbox is owned by root and other users can't create files there. So I can install a subdir, but then that is
not visible from the UI.

So the simplest short term solution is to configure the processes to log to stdout.