Add a mechanism for python test server to exit

Add a mechanism for python test server to exit

This CL adds a mechanism which can be used to make the python test server exit.

BUG=417684
Committed: https://crrev.com/6699be349706926722f7834ef1158740203eb556
Cr-Commit-Position: refs/heads/master@{#296920}

[kaliamoorthi, 2014-09-26 09:16:50]

kaliamoorthi@chromium.org changed reviewers:
+ pastarmovj@chromium.org

[kaliamoorthi, 2014-09-26 09:16:50]

PTAL

[kaliamoorthi, 2014-09-26 09:43:56]

I fixed the issues we discussed offline.

[kaliamoorthi, 2014-09-26 09:44:05]

PTAL

[pastarmovj, 2014-09-26 11:18:31]

lgtm

[kaliamoorthi, 2014-09-26 11:23:55]

The CQ bit was checked by kaliamoorthi@chromium.org

[commit-bot: I haz the power, 2014-09-26 11:24:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/607823002/20001

[commit-bot: I haz the power, 2014-09-26 11:58:09]

Committed patchset #2 (id:20001) as cc7e861ddb870db626703c9a1d1d4e19b618e418

[commit-bot: I haz the power, 2014-09-26 11:58:50]

Patchset 2 (id:??) landed as
https://crrev.com/6699be349706926722f7834ef1158740203eb556
Cr-Commit-Position: refs/heads/master@{#296920}