Use attribute from rabbitmq node to get rabbitmq IP address

The rabbitmq cookbook saves the IP address used by rabbitmq to listen,
so no need to do some fancy thing to get it.
Use helper from database cookbook to get database IP address

This way we're ready for when HA will be used for database.
Drop common recipe

It's just duplicating things done in the server recipe.
Merge pull request #47 from vuntz/db-ha

Get ready for HA in database and rabbitmq
Configure Heat's metadata, waitcondition and cloudwatch server

Those urls were wrong in 100% of the cases. use the publicURL
of the corresponding Heat services instead.
Create Keystone role for Heat Stacks

The Heat CFN managed servers use a separate keystone
role that needs to be created before it can be used.