Fix DiG query retry and fail-over bug

When the `send_done()` callback function gets called with a failure
result code, DiG erroneously cancels the lookup.

Stop canceling the lookup and give DiG a chance to retry the failed
query, or fail-over to another server, using the logic implemented in
the `recv_done()` callback function.

(cherry picked from commit c2329dd110)

bin/dig/dighost.c

@@ -2705,7 +2705,6 @@ send_done(isc_nmhandle_t *handle, isc_result_t eresult, void *arg) {
 		return;
 	} else if (eresult != ISC_R_SUCCESS) {
 		debug("send failed: %s", isc_result_totext(eresult));
-		cancel_lookup(l);
 		query_detach(&query);
 		lookup_detach(&l);
 		UNLOCK_LOOKUP;