setup: require secure_connections from foolscap

setup: require secure_connections from foolscap
This causes a problem on debian sid, since the pyOpenSSL v0.6 .deb doesn't come
with .egg-info, so setuptools will not know that it is already installed and
will try to install pyOpenSSL, and if it installs pyOpenSSL v0.7, then this
will trigger the bug in Twisted v8.1.0 when used with pyOpenSSL v0.7.

http://twistedmatrix.com/trac/ticket/3218

Now the comments in twisted #3218 suggest that it happens only with the select
reactor, so maybe using --reactor=poll will avoid it.