Switch from using the vnode interlock to a private mutex in fifo_open() to avoid lock order problems when manipulating the sockets associated with the fifo.
Switch from using the vnode interlock to a private mutex in fifo_open()
to avoid lock order problems when manipulating the sockets associated
with the fifo.

Minor optimization of a couple of calls to fifo_cleanup() from
fifo_open().

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