Curl 7.58 CPU high usage problem

[Sunhyung Lee]

Refer to https://github.com/aws/aws-sdk-cpp/issues/1253

I found HTTP request issue when I was testing my application which does long polling a certain REST API for every 100ms and after some duration of time, CPU spikes up to 100% because of curl.
For the clear test, I made simple HTTP request application which is in the link above and ran it with curl 7.58 and curl 7.66 the latest.
The sample application also shown same problem with curl 7.58 but worked fine with curl 7.66 the latest.
This test has done with Docker Ubuntu 18.04 LTS and Ubuntu 18.04 LTS in WSL.