FreeSWITCH

task scheduler: Wait for timeout, rather than fix amount in loop.

Rather than spin the task thread loop every half second, calculate the
longest the loop can wait an wait on the condition variable for that
amount. This reduces unneeded spins of the loop and actually improves
latency of some tasks. If a task becomes ready after having being
iterated over, but before main loop body is entered, previously a delay
of a half second always occured. Now, the loop will simply not wait and
iterate again.