Fixed some webui issues introduced by resource monitoring.

From: Ben Mahler <benjamin.mahler@gmail.com>
Review: https://reviews.apache.org/r/9633

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1450892 13f79535-47bb-0310-9956-ffa450edef68
Added ResourceMonitor unit tests.

From: Ben Mahler <benjamin.mahler@gmail.com>
Review: https://reviews.apache.org/r/9636

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1450893 13f79535-47bb-0310-9956-ffa450edef68
Added success logging for resource collection, and
fixed a monitoring issue caused by a gcc bug.

From: Ben Mahler <benjamin.mahler@gmail.com>
Review: https://reviews.apache.org/r/9640

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1450894 13f79535-47bb-0310-9956-ffa450edef68