Fix semantic error in example config.

The user list is meant to be a list, not a literal.

Change-Id: I56fe64660c4a45aacdab7c4b2454d46ce7e80631
Correct launch README.

The repository should be checked out on the master, not in any
arbitrary location.

Change-Id: I4cd158d205ae57e6768e522fb733910adf31bba4
Make root-only information clear in sysadmin.rst.

As we document more fully, it has become clear that the sysadmin page
really has two audiences: openstack-ci contributors and
openstack-ci/cloned-infra root operators.

Change-Id: If82c20a6292048f4212aac293da0b284f3b91436
Merge "Fix semantic error in example config."
Merge "Correct launch README."
Merge "Make root-only information clear in sysadmin.rst."