Allow subnet name in lb-vip-create and lb-pool-create

Fix bug 1168998

Change-Id: I25bf357d069b99db467db43900d293f30c2a7d30
Support router-interface-add/delete by port_id

Fixes bug 1061638

Change-Id: Ie36126a38627a6707e82116fb6b7bd97755f8fd0
Merge "Support router-interface-add/delete by port_id"
Merge "Allow subnet name in lb-vip-create and lb-pool-create"