Added support for s3/s3n to the mesos fetcher.

Review: https://reviews.apache.org/r/21852
Fix for web UI redirect message not showing up.

There was a bug that caused the "We're redirecting you to the leader"
message to not show up when visiting the web UI on a follower. Looks
to me like it was caused by an upgrade in twitter bootstrap, either
way it's a simple fix. I also changed the style from error to warning,
since the red message seemed a little harsh.

Review: https://reviews.apache.org/r/21850
Fixed compiler errors in routing library when an old glibc is used.

Review: https://reviews.apache.org/r/21822
Returned false in link::remove() if NLE_NODEV is received.

Review: https://reviews.apache.org/r/21823
Fixed the flaky SlaveRecovery MultipleFrameworks test.

Review: https://reviews.apache.org/r/21871
Fixed ExternalContainerizer wait behavior when getting destroyed.

When 'wait' was terminated by 'destroy', it is getting SIGKILLed. We
need to test for that specific case and setup the appropriate
Termination message accordingly as it can not get delivered by the
external containerizer program itself.

Review: https://reviews.apache.org/r/21681