clear /dev/kvm acls on install, and don't rmmod at qemu-kvm stop

* Make sure /dev/kvm gets its acls cleared:
 - Add acl to qemu-system.depends
 - update qemu-system.udev to run setfacl to set g::rw acl
* qemu-system.qemu-kvm.conf: don't rmmod at stop - as mtokarev points
out, the modules no longer interfere with virtualbox (etc).

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>