Check if datatype is supported for Meta commands

For the following commands:
- SET_WITH_META
- ADD_WITH_META
- SET_RET_META
- ADD_RET_META
We need to inspect the document for JSONness
only if datatype isn't supported for the connection.

Change-Id:I51331552b21d97243ec5a94549efb917b65e179e
Reviewed-on: http://review.couchbase.org/36738
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>