puffs - status report 2

[Tatsiana Severyna]

Hello,

Since now puffs can be mounted/unmounted. I've fixed plenty of bugs to
get it working last week (from commit log):
* Push vnode locking down to puffs_getvnode and puffs_makeroot
* Change puffs_cookie2vnode to use vnode lock flag
* Change state PUFFSTAT_MOUNTING -> PUFFSTAT_RUNNING in
puffs_vfsop_root (as there is no vfs_start)
* kqueue fixes
* Fix freeze during unmounting
* Don't forget to insert putter instance into list
* Use nmount in libpuffs

But most of vnode operations are still too unstable. I do not code a
lot at this point, the work is mostly about debugging. Next goal for
me is to fix rest of vops in puffs.