LUDOC-125 lnet: Add Remote Network Hash Table Size Parameter

LUDOC-125 lnet: Add Remote Network Hash Table Size Parameter

Change LU-2466 added a new module parameter: rnet_htable_size
to let the user optimize the size of the LNet remote networks
hash table.

This change is to document rnet_htable_size in the manual.

Signed-off-by: Doug Oucharek <doug.s.oucharek@intel.com>
Change-Id: I4e95acb752c6c1accf13307990210120cbb78c4c
Reviewed-on: http://review.whamcloud.com/5510
Tested-by: Hudson
Reviewed-by: Cliff White <cliff.white@intel.com>
Reviewed-by: Richard Henwood <richard.henwood@intel.com>