Increase default IO timeout from 10ms to 5s

Increase default IO timeout from 10ms to 5s

With the recent changes to the main loop, we no longer have unconditional
polling.  This means we can now sleep in select() for much longer than we
previously did.  This patch increases our select() sleep time from 10ms to 5s
which is effectively unlimited since we're going to wake up sooner than that
in almost all circumstances.

With this patch, I see the number of wake-ups with an idle dynamic ticks guest
drop from 80 per second to about 15 times per second.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5578 c046a42c-6fe2-441c-8c8c-71466251a162