Force creation of application listening socket

Force creation of application listening socket

If a previous mojo_shell run exited uncleanly, there may
be a unix domain socket sitting at the path that
IncomingConnectionListener wants to own and listen at.
This change destroys it, if possible, and creates a new
one.

BUG=407782
TEST=new unit test, run mojo_shell multiple times in a row with --enable-external-applications

Committed: https://crrev.com/5e0ad88bc5646fee917b0ff09283eaeb494b6ece
Cr-Commit-Position: refs/heads/master@{#297271}

[Chris Masone, 2014-09-29 20:17:11]

PTAL

[Chris Masone, 2014-09-29 20:17:23]

cmasone@chromium.org changed reviewers:
+ davemoore@chromium.org

[Chris Masone, 2014-09-29 20:17:42]

PTAL. I guess that git cl owners thing doesn't work like I think it does...

[DaveMoore, 2014-09-29 20:19:56]

lgtm

[Chris Masone, 2014-09-29 20:26:30]

The CQ bit was checked by cmasone@chromium.org

[commit-bot: I haz the power, 2014-09-29 20:27:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/611833005/1

[commit-bot: I haz the power, 2014-09-29 21:21:36]

Committed patchset #1 (id:1) as dce5f056991043606e3330452f2c24aea67becc9

[commit-bot: I haz the power, 2014-09-29 21:25:36]

Patchset 1 (id:??) landed as
https://crrev.com/5e0ad88bc5646fee917b0ff09283eaeb494b6ece
Cr-Commit-Position: refs/heads/master@{#297271}