Task/Improvement: Metrics::Notify80211Disconnect code improvements
Task/Improvement: Metrics::Notify80211Disconnect code improvements

(a) Remove incorrect comment: 
Metrics::Notify80211Disconnect has an incorrect comment about removing the IEEE_80211::WiFiReasonCode dependency, which cannot and should not be removed. Remove the comment. 
Metrics::WiFiStatusCode merely provides data about whether the message/action originated at the client, AP or user. It does not provide fine-grained reason codes, for which we must resort to IEEE_80211::WiFiReasonCode.

(b) Provide correct classification for wifi reason codes not listed in the current switch() statement. 
Many reason codes listed in enum WiFiReasonCode in net/ieee80211.h in shill are not covered in Metrics::Notify80211Disconnect and are hence bucketized in the default of 'kStatusCodeTypeByClient'. Check if this is correct. If not, add them to the switch statement.