Support MultiThreadIoEventLoopGroup for Netty 4.2+ compatibility#2170

dduttaCodePractice wants to merge 2 commits intoAsyncHttpClient:mainAsyncHttpClient/async-http-client:mainfrom

dduttaCodePractice:fix/support-netty-4.2-multithreadio-eventloopgroupdduttaCodePractice/async-http-client:fix/support-netty-4.2-multithreadio-eventloopgroupCopy head branch name to clipboard