Initialize metadata devices

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Refactor chain creation and retrieval

Put creator and gettor for router chains in
openstack.ChainManager.

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Set port translation for metadata server support

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Link to metadata router upon router creation

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Add a route for metadata traffic

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Clean up metadata router port upon router deletion

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>
Configure route for subnet in metadata router

Add a route for the subnet in metadata router when
router-interface-add is called. Remove the router when
router-interface-delete is called.

Signed-off-by: Tomoe Sugihara <tomoe@midokura.com>