python3: Restore original str()s where six.binary_type shouldn't be used
python3: Restore original str()s where six.binary_type shouldn't be used

This partially reverts 227b8fd984fc2fa5a37b4d8ae5d64dbd8166cc18.
These tests are testing __str__ method and shouldn't have been changed.

Signed-off-by: IWAMOTO Toshihiro <8e41ae29694291a01b8efca6b4a0005a87ddb93e@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

pichuang/ryu,habibiefaried/ryu,OpenState-SDN/ryu,hisaharu/ryu,takahashiminoru/ryu,lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext,darjus-amzn/ryu,zangree/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,John-Lin/ryu,OpenState-SDN/ryu,sivaramakrishnansr/ryu,Zouyiran/ryu,hisaharu/ryu,darjus-amzn/ryu,shinpeimuraoka/ryu,gareging/SDN_Framework,OpenState-SDN/ryu,elahejalalpour/ELRyu,elahejalalpour/ELRyu,takahashiminoru/ryu,pichuang/ryu,Tejas-Subramanya/RYU_MEC,iwaseyusuke/ryu,pichuang/ryu,fujita/ryu,John-Lin/ryu,lagopus/ryu-lagopus-ext,habibiefaried/ryu,elahejalalpour/ELRyu,osrg/ryu,lsqtongxin/ryu,zangree/ryu,elahejalalpour/ELRyu,elahejalalpour/ELRyu,fkakuma/ryu,habibiefaried/ryu,iwaseyusuke/ryu,Tejas-Subramanya/RYU_MEC,habibiefaried/ryu,TakeshiTseng/ryu,zangree/ryu,fujita/ryu,darjus-amzn/ryu,diogommartins/ryu,pichuang/ryu,gareging/SDN_Framework,shinpeimuraoka/ryu,gareging/SDN_Framework,fkakuma/ryu,John-Lin/ryu,shinpeimuraoka/ryu,TakeshiTseng/ryu,sivaramakrishnansr/ryu,iwaseyusuke/ryu,Tejas-Subramanya/RYU_MEC,sivaramakrishnansr/ryu,habibiefaried/ryu,osrg/ryu,diogommartins/ryu,OpenState-SDN/ryu,takahashiminoru/ryu,fujita/ryu,John-Lin/ryu,iwaseyusuke/ryu,gareging/SDN_Framework,osrg/ryu,Zouyiran/ryu,ttsubo/ryu,zyq001/ryu,StephenKing/ryu,sivaramakrishnansr/ryu,alanquillin/ryu,shinpeimuraoka/ryu,zyq001/ryu,fkakuma/ryu,fujita/ryu,lsqtongxin/ryu,hisaharu/ryu,alanquillin/ryu,lagopus/ryu-lagopus-ext,ttsubo/ryu,diogommartins/ryu,diogommartins/ryu,darjus-amzn/ryu,StephenKing/ryu,Zouyiran/ryu,lsqtongxin/ryu,fkakuma/ryu,darjus-amzn/ryu,lsqtongxin/ryu,TakeshiTseng/ryu,fkakuma/ryu,alanquillin/ryu,osrg/ryu,osrg/ryu,hisaharu/ryu,zyq001/ryu,hisaharu/ryu,alanquillin/ryu,takahashiminoru/ryu,Zouyiran/ryu,zangree/ryu,TakeshiTseng/ryu,StephenKing/ryu,StephenKing/ryu,alanquillin/ryu,ttsubo/ryu,sivaramakrishnansr/ryu,Tejas-Subramanya/RYU_MEC,diogommartins/ryu,fujita/ryu,gareging/SDN_Framework,ttsubo/ryu,StephenKing/ryu,Zouyiran/ryu,lsqtongxin/ryu,pichuang/ryu,TakeshiTseng/ryu,OpenState-SDN/ryu,shinpeimuraoka/ryu,zyq001/ryu,zyq001/ryu,takahashiminoru/ryu,ttsubo/ryu,Tejas-Subramanya/RYU_MEC,John-Lin/ryu,zangree/ryu