[Cooker] devfs and devpts

[Borsenkow Andrej]

devfs readme recommends to not mount devpts if devfs is in use 
(actually, it recommends to disable devpts in kernel if using devfs).

We specifically mount devpts in fstab. Is it correct? May be, it should 
be moved into rc.sysinit in branch where devfs is not mounted?

-andrej