Exposed recovery errors that are encountered in non-strict
recovery mode.

Review: https://reviews.apache.org/r/13789
Added "SlaveRecoveryTest.MasterFailover" test.

From: Jiang Yan Xu <yan@jxu.me>
Review: https://reviews.apache.org/r/13747
Added SlaveRecoveryTest.MultipleFrameworks test.

From: Jiang Yan Xu <yan@jxu.me>
Review: https://reviews.apache.org/r/13786
Added a slave recovery test for the case of multiple slaves.

From: Jie Yu <yujie.jay@gmail.com>
Review: https://reviews.apache.org/r/13753
Added a recovery timeout for executor driver self-termination.

Review: https://reviews.apache.org/r/13791
Updated slave and master to use lambda:: consistently.

From: Ian Downes <idownes@twitter.com>
Review: https://reviews.apache.org/r/13784
Fixed a 32 bit compilation issue in files.cpp.

The call to min(ssize_t, long int) won't compile on 32 bit systems
because ssize_t resolves to int on those systems.

From: Kevin Lyda <kevin@ie.suberic.net>
Review: https://reviews.apache.org/r/13793
Upgraded ZooKeeper from 3.3.4 to 3.3.6.

From: Vinson Lee <vlee@twitter.com>
Review: https://reviews.apache.org/r/13598
Added resource checks to slave recovery tests to ensure resources
are re-offered after restarts.

From: Ian Downes <ian.downes@gmail.com>
Review: https://reviews.apache.org/r/13764
Reverted "Upgraded ZooKeeper from 3.3.4 to 3.3.6.".

This reverts commit eb1cd4a7c0ad4310f090d4f0643cf4059ac5246b.
Reverted "Added resource checks to slave recovery tests to ensure
resources are re-offered after restarts."

This reverts commit 400a88f9817bb102522b08b83dca400380ad8a9b.
Fixed os::chdir return value checking in launcher.cpp.

From: Vinson Lee <vlee@freedesktop.org>
Review: https://reviews.apache.org/r/13880
Fixed clang mismatched-tags errors in process.cpp.

From: Vinson Lee <vlee@freedesktop.org>
Review: https://reviews.apache.org/r/13879
Fixed clang return-type build error in os::sendfile.

From: Vinson Lee <vlee@freedesktop.org>
Review: https://reviews.apache.org/r/13840