(#526) Handle the exitcode of a still running task correctly

[ripienaar]

This sets the exit code to -1 for still running tasks or tasks
that never started, handles -1 in the app to correctly record running
tasks

[treydock]

Test successful:

$ mco tasks run osc_tasks::yum_update_advisory --advisories RHSA-2018:2384 -I bootsrv2-test.DOMAIN
Retrieving task metadata for task osc_tasks::yum_update_advisory from the Puppet Server
Attempting to download and run task osc_tasks::yum_update_advisory on 1 nodes

Downloading and verifying 1 file(s) from the Puppet Server to all nodes: ✓  1 / 1

Running task osc_tasks::yum_update_advisory and waiting up to 60 seconds for it to complete



Summary for task 30e9cd812eed52389732609a3c78f005

                       Task Name: osc_tasks::yum_update_advisory
                          Caller: choria=tdockendorf.mcollective
                       Completed: 0
                         Running: 1

                      Successful: 1
                          Failed: 0

                Average Run Time: 58.04s



1 nodes are still running, use 'mco tasks status 30e9cd812eed52389732609a3c78f005' to check on them later

[ripienaar]

thank you @treydock