Install Guide: Fix database access for Neutron

There's a typo in the line, it should be neutron instead
of keystone like in the line above.
Also, add line breaks at proper places.

Change-Id: Ic3e48db18f07e51d5f6559ced6f7815c8d9835c8
backport: havana
Closes-Bug: #1244450
(cherry picked from commit 814e88515e452573f85f4db4214ad294f1121f58)
Merge "Install Guide: Fix database access for Neutron" into stable/havana