Fix incorrect config of notification_driver

The 'Install the Compute agent for the Telemetry service' section
uses a wrong config of notification_drive, which is set to
non-existent ceilometer.compute.nova_driver instead of the right one:
ceilometer.compute.nova_notifier.

NOTE: This patch also fixes several content overflow problem.

Change-Id: Iacb5ae6d80f29e02fc210b07bdbca7dc92ee222e
Closes-Bug: #1268503