ssa.c: Add missing initialization of sock_access[ctrl extract]

when not access node

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
core.c: Prepare core_extract_handler for update flow for access

(not enabled yet in ssa.c or in core.c:ssa_extract_db_update_prepare
where call to ssa_extract_send_db_update_prepare is #if 0'd out for now)

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: In ssa_[start stop]_access, only deal with sock_accessextract when core node

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