Move parts of the commit log for r166167, where Tor explained the interaction between vnode locks and vfs_busy(), into comment.
Move parts of the commit log for r166167, where Tor explained the
interaction between vnode locks and vfs_busy(), into comment.

MFC after:	1 week

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase