ssa.c: Reset conn_dataup.epoch to DB_EPOCH_INVALID for consumers (ACMs)

In case of new connection established with upstream node,
ensure conn_dataup epoch value is DB_EPOCH_INVALID.

Currently, this is necessary for consumer nodes that are
assigned with a new access parent, after they were connected
to some other access node.

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