Add inline docs for common.yaml
Add inline docs for common.yaml

The common.yaml file lacks inline documentation, which makes it harder
for users to understand.  This patch adds inline documentation to
make the file more self-documenting.

Change-Id: Iba98f2a829ff9b5b8ae6d2242544f0507866567c
Partial-Bug: #1270381

michaeltchapman/puppet_openstack_builder,phchoic/puppet_openstack_builder,michaeltchapman/puppet_openstack_builder,michaeltchapman/vagrant-consul,michaeltchapman/puppet_openstack_builder,CiscoSystems/puppet_openstack_builder,michaeltchapman/vagrant-consul,phchoic/puppet_openstack_builder,phchoic/puppet_openstack_builder,CiscoSystems/puppet_openstack_builder