Update instrumentation middleware so we correctly track timing info for stream requests.
Update instrumentation middleware so we correctly track timing info for
stream requests.

Previously we didn't correctly record timing for long running stream
requests (middleware returns immediately and not at the end of
response).

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