Use database alias for link disambiguation in cf-networking
Use database alias for link disambiguation in cf-networking

- The policy server consumes links of type database
- The type database is provided by both the mysql proxy and the mysql
  node
- bosh can't decide which link to use to fill the link required by
  policy server
- So we need to use the alias instead

[#145059545]

emalm/cf-deployment,cloudfoundry/cf-deployment,cloudfoundry/cf-deployment