Add dependency on Router External Gateway property

FIP has dependecy for RouterGateway resource, but it was deperecated in
favor of Router property. So we should add corrsponding dependency for
FIP resource.

Change-Id: I5c45ddc96b17bb1f87188ae3e9aabf74e6e29e1d
Closes-Bug: #1399699
Merge "Add dependency on Router External Gateway property"