Using Keep-Alive would change the timing for already established
connections. Previous to this commit, Keep-Alive worked only when using
a response_string_match due to failure to close the request body.
* Add in support for looking for substring in response
* Add note to CHANGELOG.md
* Switch from substring match to regex match
* Requested code changes
* Make requested changes and refactor to avoid nested if-else.
* Convert tabs to space and compile regex once
Also changing the net_response and http_response plugins to only accept
duration strings for their timeout parameters. This is a breaking config
file change.
closes#1214