Don't install virtualenv as user.

[FedericoRessi]

Package installation as user would fail in the case python is running inside an user virtualenv. I personally think this playbook should limit to check virtualenv is installed more than actually installing it because it is out of its scope. Most of the time virtualenv is already installed in a machine where python is installed. Some time it is not and for such few cases a regular "pip install virtualenv" should be enough. Once virtualenv is installed, I think we should install packages inside virtualenvs specific for tools to be installed instead of using --user. The reason is installing tools as root or as user has the same problem of not taking in account two or more tools could have non compatible requirements and for such cases, virtualenv is the right solution.

[obaranov]

@FedericoRessi, Can you please provide more info why you you need that change, cause we recently switched to the --user mode installation? Also looks like you're from redhat. Can you please submit patches to the gerrithub? See details here: http://infrared.readthedocs.io/en/latest/contribute.html#red-hatters