As part of resquery_response() refactoring [1], a goto statement was
replaced [2] with a call to a new function - originally called
rctx_delegation(), now folded into rctx_answer_none() - extracted from
existing code.  However, one call site of that refactored function does
not reset the "result" variable, causing a referral with a non-empty
ANSWER section to be inadvertently treated as an error, which prevents
resolution of names reliant on servers sending such responses.  Fix by
resetting the "result" variable to ISC_R_SUCCESS when a response
containing a non-empty ANSWER section can be treated as a delegation.

[1] see RT #45362

[2] see commit e1380a16741a3b4a57e54d7a9ce09dd12691522f