Linux: fail more gracefully when ProcessSingleton fails to bind.
Linux: fail more gracefully when ProcessSingleton fails to bind.

For users with AFS home directories, we cannot create UNIX domain
sockets for ProcessSingleton. Before this patch we would spin because
the socket would be constantly 'readable' for accept.

http://codereview.chromium.org/139008

BUG=14237


git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@19178 0039d316-1c4b-4281-b951-d872f2087c98

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