Attempt to catch unhandled requests in core

For some types of requests, like QueryRequests, if the environment has not explicitely been configured to activate the feature but nevertheless a QueryRequest is sent to the core, it will never receive a response.

Investigate if this is indeed due to the lack of an handler, or possibly something else (retry infinite loop)?
Attempt to fail fast in these cases, returning a generic error CouchbaseResponse (maybe at RequestHandler level, or at Locator level).

Context: integration test on Query, forgot to activate the feature via -D jvm param, test would run forever.