Unit test - storing JSON string is stored as JSON in Couchbase

Change-Id: Ieed627a82c961b178d7c25c0af07d9edd3292453
Reviewed-on: http://review.couchbase.org/43618
Reviewed-by: Simon Baslé <simon@couchbase.com>
Reviewed-by: Jeffry Morris <jeffrymorris@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>