Previously,the mesos bay type did not support the Magnum Container
Volume Model. This patch adds support for volume through the following:
1. Add username, tenant_name, preempt, region_name, domain_name to
mesos bay type.
2. Add get_parameter to mesos.
3. Update mesos unit tests to support container volume.
4. Update mesos heat templates for container volume model
Change-Id: Icf7cb9fc38c7facb2d49904b6e52bbce974948f7
Partially-Implements: blueprint magnum-integrate-with-cinder