Randomize announce interval

[titer]

I have a tracker with several thousand peers. When my tracker down for whatever reason and comes up again all the peers come back they hit them hard because they come more or less all in one minute. But the bad thing is, that they ALL come back again five minutes later because they running the SAME timer.

[brent]

Remember to deal with the first condition in tracker.c's shouldConnect - 10 second retries if tracker is unreachable.

[brent]

Added some tr_rand() to shouldConnect. Based on patch for ticket 71 that adds min_interval.

[brent]

Only call tr_rand() once. Check condition against tc->tor_finished. (I'd still like to know the proper way of checking for not-seeding state.)

[brent]

No functional change. Updated for new context.

[brent]

Updated for context

[oleo]

Following Brent ideas on r1152 - MIN/MAX runtime is not very clever way to do it.

[livings124]

In the patches, the random offset is reset after each check. Since this function is called so frequently, eventually it'll be a small enough number. The random offset value would make more sense if it wasn't set each check.

[livings124]

Done in [1242]