Update tripleo-common's project description
Update tripleo-common's project description

The Tuskar UI project is retired [1] and tripleo-common is now used to
connect the CLI and the new TripleO UI [2].

[1] https://github.com/openstack/tuskar-ui/blob/master/README
[2] https://github.com/openstack/tripleo-ui

Change-Id: I8aaca803fa254a3bf7b11eab6f9cb406f1212f6a

Tesora/tesora-project-config,openstack-infra/project-config,Tesora/tesora-project-config,openstack-infra/project-config