LU-9098 lnet: Move lnet_routes.conf to /etc

LU-9098 lnet: Move lnet_routes.conf to /etc

lustre_routes_config now skips lines which are blank or
have a first non-whitespace character of #. This enables
comments to be placed in /etc/lnet_routes.conf. Also,
provide a sample lnet_routes.conf.

The SysV lnet script now expects lnet_routes to be
in /etc. Updated docs to reflect the new location.

Test-Parameters: trivial
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Change-Id: Ie2fdc5c870aeb8165fd9896bc91120731db45c8b
Reviewed-on: https://review.whamcloud.com/25358
Tested-by: Jenkins
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Sonia Sharma <sonia.sharma@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>