ssa.c: Cosmetic change to log message

Signed-off-by: Hal Rosenstock <hal@mellanox.com>
ssa.c: In ssa_downstream_handler, be more rigorous about epoch length check

Check against proper size rather than != 0
Also, log message when it's not proper/expected length

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