Amended config instructions for cinder.config

Changed instructions from editing the [database] section to editing the
[DEFAULT] section, and slightly amended parameter.

Change-Id: I3cb6a59f7ea41486dbdf66611797f58eea3be1a3
backport: havana
Closes-Bug: #1245880
Added configuration for OpenVswitch plugin installation

Closes-Bug:#1259770

Change-Id: Iafcf9593e6b75e4bdcbb1cdfce5291cfc5ce6704
backport:havana
Merge "Amended config instructions for cinder.config"
Merge "Added configuration for OpenVswitch plugin installation"