revert previous change in cond var waiter move
revert previous change in cond var waiter move

using swap has a race condition: the waiters must be added to the
mutex waiter count *before* they are taken off the cond var waiter
count, or wake events can be lost.

chardi/musl,davidlazar/musl,chardi/musl,chardi/musl,davidlazar/musl