LU-2466 lnet: Use Hash Table for Remote Route List

This change updates the remote route list (the_lnet.ln_remote_nets)
to be a hash table (the_lnet.ln_remote_nets_hash) to speed up
access when dealing with a large number of routes (over 1000).

Signed-off-by: Doug Oucharek <doug.s.oucharek@intel.com>
Change-Id: I2dac8075ff38d29bd38905b5b1b002603c5a56b6
Reviewed-on: http://review.whamcloud.com/5023
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Tested-by: Hudson
Reviewed-by: John Hammond <john.hammond@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>