Freeze netd AIDL interface (framework)

This freezes the interface as of the latest beta build, although it has
not changed since then.
This change adds the necessary implementations for getInterfaceVersion.

Test: flashed, WiFi working
Bug: 128803828
Merged-In: Ib852b0555f0e20b858f9dd0b16dbd98dbbd22b55
Merged-In: I0c231bdce89474b53603cc15d55787c8c78a809d
(cherry picked from commit fd4eafe8)

Change-Id: Idc0e7ea98dbf57e07ee578bc1772c2111af2e563