Changed the default cgroup hierarcy path in slave
flags to "/cgroup".

From: Ben Mahler <benjamin.mahler@gmail.com>
Review: https://reviews.apache.org/r/9791

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1454610 13f79535-47bb-0310-9956-ffa450edef68
Changed command executor id to use task id.

From: Ben Mahler <benjamin.mahler@gmail.com>
Review: https://reviews.apache.org/r/9792

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1454611 13f79535-47bb-0310-9956-ffa450edef68
Fixed cgroups isolation module to close the lock
file on finalize and cleaned up cgroups tests.

Review: https://reviews.apache.org/r/9806

git-svn-id: https://svn.apache.org/repos/asf/incubator/mesos/trunk@1454612 13f79535-47bb-0310-9956-ffa450edef68