error handling fix

[mfateev]

I see cancellation working fine. But the code that catches activity exception mishandles it.

After this fixes the test fails with:

Caused by: io.temporal.common.converter.DataConverterException: com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind.MappingJsonFactory["_objectCodec"]->com.fasterxml.jackson.databind.ObjectMapper["_jsonFactory"]->com.fasterxml.jackson.databind

I'm not sure what type of object goes through the mapper.