InterfaceConfiguration: Don't use @hide Sets class

InterfaceConfiguration class is going to be jar-jar'ed by wifi (in
internal master). Remove this @hide usage to avoid transitive @hide
dependency on wifi mainline module.

Bug: 145904524
Test: Compiles
Change-Id: I4dbe69a8597d75d19fb12b4f4940b26b64fda35e