LU-9121 lnet: User Defined Selection Policy (UDSP)

User Defined Selection Policies (UDSP) are introduced to add
ability of fine traffic control. The policies are instantiated
on LNet constructs and allow preference of some constructs
over others as an extension of the selection algorithm.
The order of operation is defined by the selection
algorithm logical flow:

   1. Iterate over all the networks that a peer can be reached on
      and select the best local network
      - The remote network with the highest priority is examined
        (Network Rule)
      - The local network with the highest priority is selected
        (Network Rule)
      - The local NI with the highest priority is selected
        (NID Rule)
   2. If the peer is a remote peer and has no local networks,
      - then select the remote peer network with the highest
        priority (Network Rule)
      - Select the highest priority remote peer_ni on the network
        selected (NID Rule)
      - Now that the peer's network and NI are decided, select
        the router in round robin from the peer NI's preferred
        router list. (Router Rule)
      - Select the highest priority local NI on the local net of the
        selected route.
        (NID Rule)
   3. Otherwise for local peers, select the peer_ni from the peer.
      - highest priority peer NI is selected
        (NID Rule)
      - Select the peer NI which has the local NI selected on its
        preferred list.
        (NID Pair Rule)

   Accordingly, the User Interface allows for the following:
   - Adding a local network udsp: if multiple local networks are
     available, each one can have a priority.
   - Adding a local NID udsp: after a local network is chosen,
     if there are multiple NIs, each one can have a priority.
   - Adding a remote NID udsp: assign priority to a peer NID.
   - Adding a NID pair udsp: allows to specify local NIDs
     to be added on the list on the specified peer NIs
     When selecting a peer NI, the one with the
     local NID being used on its list is preferred.
   - Adding a Router udsp: similar to the NID pair udsp.
     Specified router NIDs are added on the list on the specified
     peer NIs. When sending to a remote peer, remote net is selected
     and the peer NID is selected. The router which has its nid on
     the peer NI list is preferred.

Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I0d94d160bdb8c09c1cf467f1c155e14ab761a47e