Docker image cleanup

Docker image cleanup

 - Renamed docker image 'opnfv/yardstick-ci' -> 'opnfv/yardstick'
   as recommended by project.
 - Added cirros image and releng repo to docker image in order to
   make it more usable in offline mode.
 - Renamed run_benchmarks to run_tests.sh
 - Moved some environment setups to a new file prepare_env.sh
 - Added daily test suites file for ericsson and LF pods.

Docker image is now built and pushed by releng script:
https://gerrit.opnfv.org/gerrit/gitweb?p=releng.git;a=blob;f=jjb/opnfv/opnfv-docker.sh

The ci/docker/Makefile file is not used by releng to build yardstick
image but the makefile can still be used to build and test docker
images locally.

Change-Id: If9d6740b39e91d145c587d8d5e2bd372d09a46a9
Signed-off-by: Jo¶rgen Karlsson <jorgen.w.karlsson@ericsson.com>