WebUI: Use slave hostname rather than libprocess.

It's safer to use the hostname of the slave rather than the libprocess
IP since we don't necessarily know that the interface's IP is publicly
accessible.  This applies especially for services like EC2.

Review: https://reviews.apache.org/r/11813
Fixed libprocess tests to write to stderr when using newer versions
of autotools.

Review: https://reviews.apache.org/r/11877
Fixed mesos tests to write to stderr when using newer versions of
autotools.

Review: https://reviews.apache.org/r/11878
Fixed a bug in the Slave's logging.
Added logging for failed detection of system resources in the slave.

Review: https://reviews.apache.org/r/11885
Update deploy scripts.

This modifies the deploy scripts to work now that --conf is not
longer supported. Instead, the deploy scripts source mesos-master-env.sh
and mesos-slave-env.sh files to pass environment variables to
the masters and slaves.

Review: https://reviews.apache.org/r/11891/
Added os::sysctl to stout.

Review: https://reviews.apache.org/r/11895