Remove VIF<->Network FK dependancy
Remove VIF<->Network FK dependancy

Related to blueprint untie-nova-network-models.

Depends-On: I665f402fe0ab1b301ab6761e80b11b101656065e
Change-Id: I9bfb957effe0a2420c312add1cca5d7af509579d

n0ano/ganttclient