Removed docker version requirement

Change-Id: I9f04db46706bf6453def09ca1e22e0db918d811b
Closes-Bug: #1237581

Conflicts:
	tools/docker/install_docker.sh
Removed dependency from dotcloud repos for the Nova docker driver

Since the Nova driver is in Nova core from the Havana release, this
will just clean the docker nova driver install.

Change-Id: Ic98012b8b5e54e727a1b11f4d32f6623d2067621
removed unecessary lines for docker install

* script was trying to copy file from a source
	that doesn't exist to destination that does.
* variable DOCKER_BRANCH no longer used.

Change-Id: I50fd55e97dfc4eaaa3c1f2bfc42e8cfc0e76cdf4