Add initial data/database transfer

Mostly complete implementation of database transfer state machines
per Ilya's recent flow diagrams

As no SSA DB yet available, used ssa_downstream_test_send to simulate
several of the transfers. That will be removed at next step in
implementation process.

What remains is to glue the database transfer to the SSA DB on both
the server and client sides.

Also, there is more code factoring to be done.

Also, message is sent to ACM when SSA DB transfer is complete so
SSA DB can put loaded into the PR GID and LID caches.

Signed-off-by: Hal Rosenstock <hal@mellanox.com>