requeue_lookup() on the canceled lookup. Because cancel_lookup()
resets the retry count of the lookup to zero, the requeued lookups
would not be retried at all (for example, in the case of UDP NS
queries executed when doing "dig +search") or, in the case of TCP
queries, retried indefinitely since the unsigned retry count of zero
was subsequently decremented, causing it to wrap around to the largest
unsigned integer value.
[RT #1940]
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