random() has returned the same result four times in a row

at least three times since we enabled the test suite.  The odds
of that happening *should* be one in a million, but NetBSD managed
to fail this time (don't remember previous times, and not sure
how to find them).

For now, I'll just change this so there's a one in a trillion chance.

exec/tests/global/random.js

 random();
-if (random() == random() == random() == random())
+if (random(10000) == random(10000) == random(10000) == random(10000))
 	throw new Error("Four random() calls returned same result");
 for (var i = 0; i < 1000; i++) {
 	var rval = random(10);