Clear and restore the calling ID.

Clear and restore the calling identity in IPC methods after asserting
the caller has the required permissions.

Fixed 2 tests in NetworkScoreServiceTest that were failing due to a
recent refactor.

Test: runtest frameworks-services -c com.android.server.NetworkScoreServiceTest
BUG: 33781319
Change-Id: I562713df3d9455cdc02bf80a687940fb9daecd8f
Merged-In: Icd79751d12dcfe4af8026980aaa1f7bd463468dc