Add database relationship between router and ports

Add an explicit schema relationship between a router and its ports. This
change ensures referential integrity among the entities and prevents orphaned
ports.

Change-Id: I09e8a694cdff7f64a642a39b45cbd12422132806
Closes-Bug: #1378866
(cherry picked from commit 93012915a3445a8ac8a0b30b702df30febbbb728)
Add Juno release milestone

Change-Id: Iea584b00329d9474c14847db958f8743d4058525
Closes-Bug: #1378855
(cherry picked from commit 4e8a5b7de71ba6f8c050c424613c025310498940)