SoundManager changes zone building RNG

[John Snail]

SoundManager._PlayWorldSound uses AudioClipSet.next to play a random sound in a set. The RNG used for this randomisation defaults to Calc.R, which appears to be used in zone building. Zone building happens on a different thread, meaning sounds can end up playing at unpredictable times during the process, changing the RNG.

Thankfully, the fix is to simply pass Rnd2 to the ShuffleInPlace call.

[Brian Bucklew]

actually uses an isolated rng here, probably something else