gresolv: Avoid accessing already freed memory

gresolv: Avoid accessing already freed memory

We must remove the lookup from lookup queue and query from query queue
before calling user callback. The callback might unref the GResolv which in
turn would remove the lookup/query what we are trying to access after
the callback is returned.

So it is enough to remove the lookup or query entry from queue before
cb is called and then manually remove it after the callback has returned.