Cannot associate multiple service-instances to PNFs

Currently the DB Edge rules for v10 and v11 have a multiplicity of OneToMany for service-instance->pnf. This does not take into account circumstances, for example, where a common border router modeled as a pnf can be used by many different enterprise service-instances. 

A change to the edge rules in aai-core should be made to accommodate a ManyToMany relationship between service-instance->pnf.