Docker definitely seems to have some network issues. I managed to fix this problem with
systemctl restart docker
... which is basically just the unix-level 'restart-the-daemon' command in Debian 8.
I had similar problem. But as I was running AWS linux i had no systemctl. I solved using:
sudo service docker restart
My docker build also failed while trying to run apt-get upgrade with the exact same errors. I was using docker-machine on Mac OSX and a simple docker-machine restart default solved this issue. No idea what initially caused this, though.
apt-get upgrade
docker-machine restart default