git: kernel - misc MPSAFe work

[Matthew Dillon]

:I wonder if the change below is really neccessary, as LIST_INSERT_HEAD is
:not MP-safe and
:the whole function kern_jail must be called with mp_lock hold. It just made
:me think that you missed
:to make the list insert race free until I saw that the function is always
:called with mp_lock held.

    Yah, you're right.  There's no need to use atomic ops on prisoncount.
    I haven't made the jail-related system calls MPSAFE yet anyway.

						-Matt