app/ofctl: fix possible deadlock when the datapath disconnects
app/ofctl: fix possible deadlock when the datapath disconnects

Signed-off-by: Atzm Watanabe <3a850ea3d7cec79773bd07168d6cff55a42448ca@iij.ad.jp>
Reviewed-by: IWAMOTO Toshihiro <8e41ae29694291a01b8efca6b4a0005a87ddb93e@valinux.co.jp>

fujita/ryu,osrg/ryu,iwaseyusuke/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,osrg/ryu,lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext,osrg/ryu,osrg/ryu,osrg/ryu,fujita/ryu,fujita/ryu,iwaseyusuke/ryu,fujita/ryu,iwaseyusuke/ryu,fujita/ryu,iwaseyusuke/ryu,lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext