Replace string copies with const-ref am: 121fedaa46

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2869314

Change-Id: I5e99081653e109e083973770682d8b2ac0b12e59
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>