Do not send traceback to clients by default

eventlet.wsgi.server contains a "debug" param which is True by default.
This sends tracebacks to the client on 500 errors, which is not
desirable for security reasons.

Set this to be False by default.

Fixes bug 1192132

Change-Id: Ib54fb79128c6922f7a38339c4256f0e4c81e1665
Merge "Do not send traceback to clients by default"