Workaround the panic, triggered by the netgraph attempting to

Workaround the panic, triggered by the netgraph attempting to
load a missing module from within the socket dispatch thread, by:

- not trying to load a netgraph module when you can't.

- preloading ng_ksocket.ko(if missing) from the module handler
  where you're guaranteed to have the process context needed by
  the linker_* functions. This makes us sure at least that the basic
  netgraph operations will work without messing with loading a kernel
  module on the fly (suggested by: hiten@).

Reviewed-by: hiten@