Get node list information for jobs submitted with the Torque backend

[vkarak]

Sample implementation from @ZQyou:

    def _get_nodelist(self, job, jobstat):
        # exec_host = o0580/0-27+o0444/0-27+o0345/0-27
        nodelist_match = re.search('exec_host = (?P<nodelist>\S+)', jobstat.stdout)
        if nodelist_match:
            nodelist = [ x.split('/')[0] for x in nodelist_match.group('nodelist').split('+') ]
            nodelist.sort()
            job.nodelist = nodelist