Remove unused methods from NetworkManagementService. am: b6a0decbc6

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2608447

Change-Id: I728c57e3469f01734c71785a99059b904c938bcd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>