dpset: Fix iteration error when disconnecting switches
dpset: Fix iteration error when disconnecting switches

When disconnecting switches, dpset will fail to unregister ports,
because size of values in the port state dictionary might be
changed when doing the iteration.
This patch fixes to copy the values list and fixes this problem.

Signed-off-by: IWASE Yusuke <bb80e84cc9f5a8f01385872ee89032beb5d4eba7@gmail.com>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

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