Model#reload refreshes the CAS value also

Change-Id: Iea51dc9a1c8635dafa4a83582d08d73069a81bcd
Reviewed-on: http://review.couchbase.org/29745
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>