Generate a unique session ID by using socket.gethostname() instead of socket.gethostbyname(), since the latter one could make bindctl stall if its own host name can't be resolved.(the patch was created by Jinmei and reviewed by zhanglikun)

git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@2096 e5f2f494-b856-4b98-b285-d166d9295462