Ideal rate manager does not work when non best-effort traffic is used

This was observed by @stavallo in the scope of the 11ax project, but this should be reproduced for any configuration TXing at least one non AC_BE traffic.

After some investigations, it appears that the reason is that the station manager holds a station structure per destination and per TID, but for Ideal, the last received SNR is always 0 for TID different than 0 (so, when it is not AC_BE).

I have a patch solving the problem, but regression tests should be extended to cover such cases.