MFC r296286,r296470,r296472,r296473,r296575:

MFC r296286,r296470,r296472,r296473,r296575:

  r296286:
    Remove filemon->lock wrappers.
  r296470:
    Only call bwillwrite() for logging to vnodes, as other fo_write() calls do.
  r296472:
    Require kldunload -f to unload.
  r296473:
    Add missing break for r296472.
  r296575:
    FILEMON_SET_FD: Disallow changing the fd.

git-svn-id: svn://svn.freebsd.org/base/stable/10@296752 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f