staging: lustre: lnet: check if ni is in current net namespace

Add new 'ni_net_ns' field to struct lnet_ni to hold a reference
to original net namespace in which ni is created.
In LNetDist(), check if ni was created in same net namespace as
current's one. If not, assign order above 0xffff0000, to make
this ni not a priority.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7845
Reviewed-on: http://review.whamcloud.com/21884
Reviewed-by: Olaf Weber <olaf@sgi.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>