Fixed protobuf::read bug exposed when running Mesos compiled by clang.

Review: https://reviews.apache.org/r/16660
Bug in http::request missing os::close.

Review: https://reviews.apache.org/r/17093

Conflicts:
	3rdparty/libprocess/src/process.cpp
Fixed slave to properly do memory isolation when executor resources
are not specified.

From: Vinod Kone <vinodkone@gmail.com>
Review: https://reviews.apache.org/r/17295