python-tornado: fix runtime dependencies

python-tornado: fix runtime dependencies

According to setup.py tornado requires backports.ssl_match_hostname
for Python < 3.2 and certifi for Python < 3.4.

Actually both requirements are optional and tornado alone can work
without them, but Python packages like python-circus check requirements
at runtime and though they don't use this funtionality, they insist on
having these packages installed.

An upstream patch fixes backports.ssl_match_hostname dependency and
selecting python-certifi for Python 2 fixes certifi dependency till
this is fixed upstream.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>