Default setting san_thin_provision should be true

Currently cinder eqlx_san_thin_provision option is false to
disable creation of thin-provisioned volumes.
The default should be true to enable thin provisioning which is the recommended setting.

There is a Openstack launchpad bug to fix documentation:
https://bugs.launchpad.net/openstack-manuals/+bug/1384927

Change-Id: I4252da3e60004998c3cd15921ac403bd8969ee57