sched: change timer state inside atomic context

timer_base is a thread-agnostic interface for per-CPU timers.  The
current code is prone to a race condition involving set() and
cancel(). The latter may attempt to remove the timer before it was
inserted into timer tree.

Found during code inspection.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
scripts/gen-vmx.sh: Reduce virtualHW version

ESXi 5.5 can not edit virtualHW.version = 10 vmx file. Reducing to 8
works in ESXi.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>