ssa.c: In ssa_upstream_update_conn, make SSA_DB_FIELD_DEFS index 5 match downstream

On downstream, it is:
ssa_downstream_handle_query_field_defs: pp_field_tables index 5 (nil) len 0 rsock 45

Now on upstream side, it is:
ssa_upstream_update_conn: SSA_DB_FIELD_DEFS index 5 (nil) len 0 rsock 30

It used to indicate len 32 on upstream side which is length of the received
SSA header.

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