Make our docker-image more user-friendly
Make our docker-image more user-friendly

- move from ubuntu:14.04 base image to ubuntu:16.04 .
  Ubuntu 16.04 is current/latest LTS release. Let's use it.

- pre-install vim
  It is a "feaute request". Users like to experiment and modify samples
  inside container.

- pre-install bash-completion
  Rally provides bash-completion script, but uit doesn't work without
  installed `bash-completion` package.

- remove '-e' from execution of `echo`.
  This flag is not required, even more it is redundant.

- add sudo rights to rally user
  Rally is a pluggable framework. External plugins can require installation
  of additional python or system packages.

Change-Id: I9540343adbb48fded5531bd3c819396cdb7328df

gluke77/rally,openstack/rally,openstack/rally,vganapath/rally,yeming233/rally,gluke77/rally,gluke77/rally,yeming233/rally,gluke77/rally,vganapath/rally,openstack/rally,openstack/rally,vganapath/rally,vganapath/rally