plugins/traffic-control: remove latency and packet loss from generic metadata
plugins/traffic-control: remove latency and packet loss from generic metadata

Latency and packet loass are displayed in the table, there is not need to
show them in the general section too.

paulbellamy/scope,weaveworks/scope,alban/scope,kinvolk/scope,alban/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope,weaveworks/scope,paulbellamy/scope,kinvolk/scope,alban/scope,paulbellamy/scope,kinvolk/scope,alban/scope,weaveworks/scope,weaveworks/scope,kinvolk/scope,alban/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope,paulbellamy/scope,alban/scope