of1.2: fix OFPSetConfig default arguments
of1.2: fix OFPSetConfig default arguments

If you use initialize like the following way:

OFPSetConfig(dp, miss_send_len=1600)

You get the following assertion when it's serialized:

File "/Users/fujita/git/ryu/ryu/ofproto/ofproto_v1_2_parser.py", line 244, in _serialize_body
  assert self.flags is not None

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

fujita/ryu,ynkjm/ryu,fujita/ryu,ysywh/ryu,o3project/ryu-oe,alanquillin/ryu,lagopus/ryu-lagopus-ext,citrix-openstack-build/ryu,ttsubo/ryu,jalilm/ryu,StephenKing/ryu,umkcdcrg01/ryu_openflow,sivaramakrishnansr/ryu,Zouyiran/ryu,iwaseyusuke/ryu,openvapour/ryu,jalilm/ryu,muzixing/ryu,lagopus/ryu-lagopus-ext,darjus-amzn/ryu,torufuru/OFPatchPanel,openvapour/ryu,lzppp/mylearning,jkoelker/ryu,muzixing/ryu,darjus-amzn/ryu,Zouyiran/ryu,elahejalalpour/ELRyu,ysywh/ryu,ynkjm/ryu,yamada-h/ryu,haniehrajabi/ryu,Zouyiran/ryu,samrussell/ryu,OpenState-SDN/ryu,umkcdcrg01/ryu_openflow,ttsubo/ryu,castroflavio/ryu,takahashiminoru/ryu,sivaramakrishnansr/ryu,osrg/ryu,haniehrajabi/ryu,lsqtongxin/ryu,zyq001/ryu,lsqtongxin/ryu,zangree/ryu,samrussell/ryu,StephenKing/summerschool-2015-ryu,fkakuma/ryu,alanquillin/ryu,gopchandani/ryu,shinpeimuraoka/ryu,unifycore/ryu,unifycore/ryu,takahashiminoru/ryu,yamt/ryu,habibiefaried/ryu,John-Lin/ryu,diogommartins/ryu,pichuang/ryu,jazzmes/ryu,StephenKing/summerschool-2015-ryu,shinpeimuraoka/ryu,alyosha1879/ryu,openvapour/ryu,sivaramakrishnansr/ryu,haniehrajabi/ryu,gareging/SDN_Framework,osrg/ryu,StephenKing/summerschool-2015-ryu,osrg/ryu,pichuang/ryu,Tesi-Luca-Davide/ryu,takahashiminoru/ryu,yamt/ryu,ynkjm/ryu,ttsubo/ryu,citrix-openstack/build-ryu,Tejas-Subramanya/RYU_MEC,TakeshiTseng/ryu,yamt/ryu,ntts-clo/mld-ryu,Tejas-Subramanya/RYU_MEC,John-Lin/ryu,diogommartins/ryu,torufuru/oolhackathon,darjus-amzn/ryu,jalilm/ryu,habibiefaried/ryu,lzppp/mylearning,mikhaelharswanto/ryu,haniehrajabi/ryu,osrg/ryu,jalilm/ryu,castroflavio/ryu,StephenKing/ryu,fkakuma/ryu,ysywh/ryu,osrg/ryu,gareging/SDN_Framework,umkcdcrg01/ryu_openflow,jkoelker/ryu,TakeshiTseng/ryu,fujita/ryu,gopchandani/ryu,torufuru/oolhackathon,ntts-clo/ryu,gareging/SDN_Framework,haniehrajabi/ryu,zangree/ryu,Tejas-Subramanya/RYU_MEC,lagopus/ryu-lagopus-ext,diogommartins/ryu,gareging/SDN_Framework,Tesi-Luca-Davide/ryu,castroflavio/ryu,lsqtongxin/ryu,citrix-openstack-build/ryu,alanquillin/ryu,fujita/ryu,yamada-h/ryu,ntts-clo/mld-ryu,gopchandani/ryu,alyosha1879/ryu,torufuru/OFPatchPanel,jazzmes/ryu,John-Lin/ryu,hisaharu/ryu,diogommartins/ryu,elahejalalpour/ELRyu,StephenKing/ryu,ttsubo/ryu,o3project/ryu-oe,ysywh/ryu,StephenKing/ryu,habibiefaried/ryu,lagopus/ryu-lagopus-ext,fkakuma/ryu,StephenKing/summerschool-2015-ryu,Zouyiran/ryu,iwaseyusuke/ryu,gopchandani/ryu,zyq001/ryu,darjus-amzn/ryu,Tesi-Luca-Davide/ryu,John-Lin/ryu,lzppp/mylearning,StephenKing/ryu,torufuru/oolhackathon,evanscottgray/ryu,lsqtongxin/ryu,OpenState-SDN/ryu,StephenKing/summerschool-2015-ryu,elahejalalpour/ELRyu,John-Lin/ryu,takahashiminoru/ryu,muzixing/ryu,lsqtongxin/ryu,ynkjm/ryu,fkakuma/ryu,openvapour/ryu,yamt/ryu,fkakuma/ryu,TakeshiTseng/ryu,iwaseyusuke/ryu,evanscottgray/ryu,shinpeimuraoka/ryu,lagopus/ryu-lagopus-ext,TakeshiTseng/ryu,Tejas-Subramanya/RYU_MEC,shinpeimuraoka/ryu,shinpeimuraoka/ryu,takahashiminoru/ryu,alyosha1879/ryu,iwaseyusuke/ryu,gareging/SDN_Framework,jkoelker/ryu,evanscottgray/ryu,iwaseyusuke/ryu,Tejas-Subramanya/RYU_MEC,zangree/ryu,citrix-openstack/build-ryu,OpenState-SDN/ryu,yamt/ryu,ttsubo/ryu,zangree/ryu,fujita/ryu,ntts-clo/ryu,mikhaelharswanto/ryu,Tesi-Luca-Davide/ryu,alanquillin/ryu,alanquillin/ryu,openvapour/ryu,hisaharu/ryu,muzixing/ryu,OpenState-SDN/ryu,sivaramakrishnansr/ryu,zyq001/ryu,lzppp/mylearning,umkcdcrg01/ryu_openflow,muzixing/ryu,hisaharu/ryu,zyq001/ryu,diogommartins/ryu,pichuang/ryu,elahejalalpour/ELRyu,zyq001/ryu,OpenState-SDN/ryu,Tesi-Luca-Davide/ryu,ysywh/ryu,zangree/ryu,lzppp/mylearning,jalilm/ryu,sivaramakrishnansr/ryu,hisaharu/ryu,elahejalalpour/ELRyu,Zouyiran/ryu,darjus-amzn/ryu,gopchandani/ryu,habibiefaried/ryu,jazzmes/ryu,habibiefaried/ryu,ynkjm/ryu,TakeshiTseng/ryu,alyosha1879/ryu,pichuang/ryu,hisaharu/ryu,umkcdcrg01/ryu_openflow,pichuang/ryu