virtualenv.managed: use "user" instead of "runas" for pip install

This commit changes the virtualenv.managed state to use "user" instead
of "runas" when it runs pip.install to satisfy a requirements file.
deprecate runas argument in virtualenv.create
Merge pull request #9497 from terminalmage/issue8190

Use "user" instead of "runas" argument when calling pip.install from virtualenv.managed state