[N1QL] update on a document created using python sdk resets flag

Document flags are reset on n1ql update even in case of a failure.

Steps to reproduce:
Create a document using python sdk with pickle serialization
ok = cb.set('odwalla-juice1',

, format=FMT_PICKLE)
is created with CAS=0xd21547caea13, Flags=0x1000001
using cbq
UPDATE default USE KEYS "odwalla-juice1" SET type="product-juice" RETURNING default.type;
This fails as the document was serialized with "msg": "Unable to SET path (`default`.`type`)"

On retrieving the document using sdk
item = cb.get('odwalla-juice1')
print(item)
ValueResult<RC=0x0, Key=u'odwalla-juice1', Value=u'KGRwMApTJ3R5cGUnCnAxClMnanVpY2UnCnAyCnMu', CAS=0xe4f951caea13, Flags=0x0>
sdk is not able to deserialize the document as the flags were reset