use old cryptography version
use old cryptography version

Looks like that the latest version (1.5.2) doesn't work:

https://s3.amazonaws.com/archive.travis-ci.org/jobs/164527154/log.txt

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

gareging/SDN_Framework,lagopus/ryu-lagopus-ext,fkakuma/ryu,TakeshiTseng/ryu,fkakuma/ryu,fkakuma/ryu,fkakuma/ryu,fujita/ryu,lagopus/ryu-lagopus-ext,fujita/ryu,TakeshiTseng/ryu,gareging/SDN_Framework,shinpeimuraoka/ryu,osrg/ryu,iwaseyusuke/ryu,fujita/ryu,pichuang/ryu,gareging/SDN_Framework,gareging/SDN_Framework,TakeshiTseng/ryu,osrg/ryu,pichuang/ryu,iwaseyusuke/ryu,iwaseyusuke/ryu,osrg/ryu,osrg/ryu,osrg/ryu,TakeshiTseng/ryu,shinpeimuraoka/ryu,lagopus/ryu-lagopus-ext,fkakuma/ryu,fujita/ryu,gareging/SDN_Framework,iwaseyusuke/ryu,lagopus/ryu-lagopus-ext,TakeshiTseng/ryu,pichuang/ryu,shinpeimuraoka/ryu,shinpeimuraoka/ryu,pichuang/ryu,iwaseyusuke/ryu,fujita/ryu,pichuang/ryu,lagopus/ryu-lagopus-ext,shinpeimuraoka/ryu