Preserve gocb error types (#3492)
Preserve gocb error types (#3492)

Fixes #3491
ceejatec/sync_gateway,ceejatec/sync_gateway,couchbaselabs/sync_gateway,couchbaselabs/sync_gateway,ceejatec/sync_gateway,couchbaselabs/sync_gateway,couchbaselabs/sync_gateway,ceejatec/sync_gateway