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

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



Change-Id: I1e87a465acf447336183df58ffb2c4e21371fcb6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>