Add config passthrough support for ironic

Adding support for passthrough config options to ironic.conf

Change-Id: Id5dfba5b40741a1fcf720ec7ca7b6017b43a6a01
Add ulimit nofile config for rabbitmq

In larger deployments the rabbitmq user will run out of file descriptors
due to the number of connections it opens. This change allows you to
modify the maximum number of file descriptors the user can have.

Change-Id: Ic691fd68c3397d392fd4a9db1ee672b1eae77b6d
Merge "Add ulimit nofile config for rabbitmq"
Merge "Add config passthrough support for ironic"