kernel - Change tcp keepalive options from ms to seconds (DISRUPTIVE)

kernel - Change tcp keepalive options from ms to seconds (DISRUPTIVE)

* Change TCP_KEEPINIT, TCP_KEEPIDLE, and TCP_KEEPINTVL units from
  milliseconds to seconds, matching most other operating system
  distributions.

  This is after the Nth time we've hit problems porting applications.

* I've decided to make this change, even though it is disruptive
  (a significant API change).  It shouldn't effect most use cases
  and it fixes things like chromium without us having to continuously
  patch the chromium sources.

* Fixes numerous too-fast-a-timeout issues with chrome.