Add target_sdk_version in NetworkStackRootTests. am: ab62fd4ada

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/2261945

Change-Id: I2f33551bfd64e01b7b7c18fec41d1e1156157773
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>