Update default db username to keystone

The current default db username for keystone is
keystone_admin. This is inconsistent with the default
db username for every other service which use the
same name as the name of the service.

The documented installation instruction for keystone
also use keystone as the database user.

This commit updates the default to use keystone instead of
keyston_admin.

Change-Id: I1cfaf3fbbc691ff9dbef415b69492f9f965dc113
Update documentation for sql_connection credentials

Lets use the same username and password the database server setups by
default.  Otherwise, following the examples will result in a password /
user mismatch.

Change-Id: Ieee67b5912bb823a3b422752bb7f7e30bbba4897
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>
Pin posgresql to 2.5.0

b/c the upstream version has broken backwards compat

Change-Id: Idf751af76b37ac8b165facc4a5f776f8804535f8
Merge "Update documentation for sql_connection credentials"
Merge "Update default db username to keystone"