arc/cli/app.py: be more careful when checking the parsed command line options

The attributes may not exist, so check if they exist before accessing them.

The comment about having better introspection still applies, and now with
the advent of specific command for different modules (say '--list-jobs' for
the host module) this becomes really urgent.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
host: Implemented --list-jobs action

That shows along the list of host, the jobs that may be running on them.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
arc/cli/actions/host.py: Fix for implementation of --list-jobs

The job ID actually comes encoded in 'jobs', then 'id'.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
arcli: show only currently running jobs by default

This is a usability change (hopefully an improvement): previously
we'd show all jobs when running:

$ arcli job -l

And only currently running jobs when running:

$ arcli job -l --running

But, based on my own experience, it's much more common to want to
see the currently running jobs. So, now, to show currently running
jobs just run:

$ arcli job -l

And to show all jobs run:

$ arcli job -l --all

Signed-off-by: Cleber Rosa <crosa@redhat.com>
arcli: allow for more natural syntax on job deletion (abortion)

Currently to abort a job one would run:

$ arcli job -d -i <JOB_ID>

Where '-d' is the delete action, and the job to be deleted is job
whose ID is given with '-i'.

This coherent with the other commands that allow one to delete, say
a host, by either name or ID precisely. The problem is that is not
really straightforward, so allow a second syntax:

$ arcli job -d <JOB_ID>

Since a job will never be deleted/aborted based on its name, but
always based on its ID.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Release: bumped version to 0.0.2

Signed-off-by: Cleber Rosa <crosa@redhat.com>