Do not use -y for package install

As a followup to a patch for basic-install (see
https://review.openstack.org/#/c/30263/), here's an update
for the rest of the manual to remove -y as option for package
installations.

See also
http://lists.openstack.org/pipermail/openstack-docs/2013-May/001787.html

Change-Id: I3d3bcfac4d3ae41933b587f026e1f1c75f02ea08
Merge "Do not use -y for package install"