Remove ref_count_obj support and replace with smdb_refcnt

As of the following commit, PRDBs are no longer reference counted:
commit 1b69ad459a0b8878fec889baedeedaa7c6b786ff
Author: Sasha Kotchubievsky <sashakot@mellanox.com>
Date:   Mon Nov 10 15:08:32 2014 +0200

    ssa.c: Decouple access and downstream threads during PRDB update

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

Since then, it is only SMDB which is reference counted. Reference
counting there is only an optimization to determine when
current SMDB is "in use" (in process of being transferred downstream).

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Reorder parameters to ssa_db_update_init to be consistent with other APIs

svc parameter comes first (before SSA DB parameter)

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: Trivial reorder of local variables in ssa_access_map_callback

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