os: Recompute whether any clients are ready after ProcessWorkQueue() (bug 98030)

If a work proc wakes up a sleeping client and it is ready to execute,
we need to re-compute the local 'are_ready' value before deciding
what timeout value to use in WaitForSomething.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98030


Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>