Remove content-length metrics.
Remove content-length metrics.

Gauge is not really the best type for it and we don't support histogram
metrics at this point.

nzlosh/st2,nzlosh/st2,Plexxi/st2,StackStorm/st2,nzlosh/st2,StackStorm/st2,StackStorm/st2,Plexxi/st2,StackStorm/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2