pefs status report 4

[Gleb Kurtsou]

Last week I've implemented correct lookup operation. Encrypted file name
can't be constructed solely from plain text name, because encrypted name
contains random tweak value and checksum. I've change code no to use
vop_bypass, as it was used only in a few places anyway, and there was
need to add additional argument to pefs_bypass -- encrypted component
name. I've disabled node recycling in vop_inactive, as pefs_node
structure is not used to store lower vnode address anymore but also
contains encryption keys. It allowed enabling of cached lookups and
doesn't force recreation of vnodes for every operation.

This week I'm planing to finish basic infrastructure work left:
introduce minimal key management and use real encryption to verify
correctness.