jobs: use count itertool instead of home made

import traceback

from threading import Thread, Event

from StringIO import StringIO

from itertools import count

from cloudcontrol.node.exc import JobError

from cloudcontrol.node.utils import num_to_sig, close_fds

        """

        :param main_loop: :class:`MainLoop` instance

        """

        def counter():

            i = 0

            while True:

                yield i

                i += 1

        self.job_id = counter()

        self.job_id = count()

        self.main = main_loop

        #: keep an index of all jobs

        self.jobs = {}