Correct cqpv log field value for tunnel connections

According to @masaori335 's comments on #7491 and #7511, it sounds like `cqpv` log field doesn't have a valid protocol name used in a tunnel. TLS partial blind tunnel ignores the issue and uses another field (`cqssa`) to log protocol names.

If we can't / don't log protocol names used in tunnels to `cqpv`, it should be documented and the value should be `-` but not misleading garbage value.

And I also think using `cqssa` as an alternative field has two problems. We should probably log protocol names to `cqpv` on tunnel connections as well.

Log size -- To collect protocol names used for the both tunnel connections and non-tunnel connections you need to log two fields, and either of them is always redundant or garbage. It unreasonably increases log size.
Readability -- Looking at different log fields depending on connection type is hard. Also `cqssa` has protocol IDs but not human friendly protocol names. It requires log readers more knowledge.