The smart scheduler is designed to minimize scheduler overhead by
increasing the interval between WaitForSomething calls when a single
client is running. However, the software rotation code depends on
its BlockHandler being invoked for screen updates; the long delays
caused by the smart scheduler optimizations means that screen updates
can be delayed a long time as well.

The change is simple -- prevent the smart scheduler from increasing
the scheduling interval while any screen is using software rotation.

Signed-off-by: Keith Packard <keithp@keithp.com>