Fix broken couchbase.{_to,_from}_json
Fix broken couchbase.{_to,_from}_json

These two methods were broken because they would just return the
function and not the actual encoded/decoded values

These methods were only used for serializing MutationStates, and
therefore were not actually tested anywhere

Change-Id: Icd74c88406525fdb8c2108e5fcdff62e67a2cff2

mnunberg/couchbase-python-client,mnunberg/couchbase-python-client