Set allow_reuse_address when spinning up devtools server.
Set allow_reuse_address when spinning up devtools server.

The TCP stack apparently puts the socket into timed-wait after the
servers shuts down. To allow rebinding the socket immediately afterwards
we need to set SO_REUSEADDR.

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/1144023004

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