I have changed /etc/default/docker
with DOCKER_OPTS=\"-H tcp://127.0.0.1:2375 -H unix:///var/run/docker.sock\"
(docker version 1.4.1 in ubuntu 14.0
I've just run into the "same" problem.
I noticed that all the options in the /etc/default/docker are actually commented out by default.
I removed the # in front of DOCKER_OPTS, restarted and it worked as intended.
I think previous docker versions (1.3) didn't have these options commented out by default, at least I can't remember having to remove the #-sign.