Do not dump metrics if reproxy was never started am: 5990257d am: 1145dd81

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/soong/+/19049587



Change-Id: Ibdf61b445a1b6b11fb81a8021945e0a849a97a6b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>