Add @localhost to openstack_citest user example

Without this, mysql can match the anonymous user first and then
rejects the openstack_citest password [1] leading to some confusing
tox output.

[1] http://bugs.mysql.com/bug.php?id=36576

TrivialFix
Change-Id: Ic9a753307960634f0e5c40abf06ec5bac92d9897
Merge "Add @localhost to openstack_citest user example"