Merge pull request #1364 from benallard/docker_absolute

Use absolute import in the docker module
DockerLatentBuildSlave:
 - Fix: create the container with the name <slavename>_<id>
 - Fix: destroy the container after the stop operation. (Eg: remove from disk)
DockerLatentBuildSlave:
 - remove the last \n of log lines when the docker image is built.
DockerLatentBuildSlave
 - remove buildFinished method. It breaks at least:
   - a slave can run several build in parallel.
     with buildFinished, the container is removed as soon as the first build is finished. As a consequence, concurrent build are canceled.
     This is not what we want
   - build_wait_timeout feature
     This is implemented by AbstractLatentBuildSlave
When using a AbstractLatentBuildSlave with build_wait_timeout >0, this tracback appears when the slave is disconnected when the build_wait_timer fired:

	Traceback (most recent call last):
	  File "/home/xavierd/Projects/myGitHub/buildbot-work/sandbox/local/lib/python2.7/site-packages/twisted/spread/pb.py", line 1341, in maybeLogout
	    fn()
	  File "/home/xavierd/Projects/myGitHub/buildbot-work/src/master/buildbot/pbmanager.py", line 177, in <lambda>
	    return (pb.IPerspective, persp, lambda: persp.detached(mind))
	  File "/home/xavierd/Projects/myGitHub/buildbot-work/src/master/buildbot/buildslave/protocols/pb.py", line 104, in detached
	    self.notifyDisconnected()
	  File "/home/xavierd/Projects/myGitHub/buildbot-work/src/master/buildbot/buildslave/protocols/base.py", line 43, in notifyDisconnected
	    self._disconnectSubs.deliver()
	--- <exception caught here> ---
	  File "/home/xavierd/Projects/myGitHub/buildbot-work/src/master/buildbot/util/subscription.py", line 37, in deliver
	    sub.callback(*args, **kwargs)
	exceptions.TypeError: _disconnected() takes exactly 1 argument (0 given)
autopep8
Merge pull request #1365 from delanne/DockerLatentFix

various minor fix for AbstractLatentBuildSlave and DockerLatentBuildSlave