Simplify & Improve Dockerfile
Simplify & Improve Dockerfile

- Remove usage of install_rally
- Remove installation of not used packages
- Remove installation of python-pip from sources
- Put DB and Config on volume in /home/rally/.rally/

Change-Id: Ib48dda24056e2930c22dda75762a8f7c4ede29c0

openstack/rally,openstack/rally,openstack/rally,openstack/rally