Netty: Autoread functional issues discovered by performance testing

[mrsaldana]

During performance testing, issues were found showing that traffic stopped under heavy stress using the Ping test scenario for the Day Trader application.

This issue will investigate by recreating the stress scenario.

Findings:

Running the script with the following configuration was enough to show errors:
warmupTime=120
runTime=120
warmup_threads=5
run_threads=5

Solution Approach:
The HttpDispatcher has already been upgraded with support for reads that contain more than one message. However, since the pipelining request handler is being removed, in addition to controlling when read operations are made, we can ensure only one message is sent down the pipeline per read operation. This should help mitigate race conditions that might corrupt the read flow states.

With the addition of the FlowControlHandler, the same script configuration is running without errors.

Changes are being handled within the autoread performance branch: mrsaldana#3

Estimated PD - 10