add INFO logs for vb creation/deletion

Change-Id: If20ab4d92a08e3eaed06b0d3dfdbfc67df3c5a50
Reviewed-on: http://review.couchbase.org/38719
Reviewed-by: Sriram Ganesan <sriram@couchbase.com>
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: Sundararaman Sridharan <sundar@couchbase.com>