use a singleton for ifaceIndexNameMap(IFACE_INDEX_NAME_MAP_PATH) am: 022b286f2b am: c5e373f0e3

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2924884

Change-Id: Ib1f6fc1eb34b7dfd4288ef499bbbf5b43748c8aa
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>