resolved: extend various timeouts

resolved: extend various timeouts

Let's increase a number of timeouts as they apparently are too short for
some real-world lookups.

See:

https://github.com/systemd/systemd/issues/4003#issuecomment-279842616

In particular we change the following timeouts:

1) The first UDP retry we increase 500ms → 750ms. This is a good idea,
   since some servers need relatively long responses for trivial lookups,
   and giving up our first attempt also has the effect of trying a
   different server for the next attempt which has the side effect that
   we'll run two down-grade iterations in parallel, on both servers.
   Hence, let's give servers a bit more time in the first iteration.

2) Permit 24 retries instead of just 16 per transactions. If we end up
   downgrading all the way down to UDP for a lookup we already need 5
   iterations for that. If we want permit a couple of lost packages for
   each (let's say 4), then we already need 20 iterations.

3) Increase the overall query timeout on the service side to 60s (from
   45s), simply because very long and slow DNSSEC + CNAME chains (such as
   us.ynuf.alipay.com) hit this boundary too easily. The client side
   timeout for the bus method call is increased to 90s, in order to have
   room for the dbus reply to go through