* Changed LNetGet() LNetPut() to include a source nid parameter

*    Changed LNetGet() LNetPut() to include a source nid parameter
     Set this to LNET_NID_ANY to have the source nid set automatically,
     otherwise it checks that the destination is reachable from the given
     source NID and sends using that.   This ensures the source NID is
     deterministic in the presence of equivalent routes.

*    Changed LNetDist() to return the count of networks traversed rather than
     routers (i.e. 0 == local, 1 == local net, 2 == via 1 router etc).  It also
     returns a source NID (== NID of local LNET interface that will send).

*    Changed LNet() completion events to include the target process ID so the app
     can tell which NID the sender sent to.

*    Removed the 'implicit_loopback' lnet module parameter.  You have to use
     0@lo explicitly if you want loopback.

*    Changed lustre to remember the source NID returned by LNetDist() to ensure
     client requests always arrive with a consistent initiator NID.

*    Changed lustre to remember the target NID of incoming requests to ensure
     server replies are always sent with the same source NID that the client
     sent her requests to.

*    Changed lustre to use a NID of 0@lo if the distance to the target NID is 0
     (i.e use the loopback LNET interface when talking to local servers).