Merge "follows the advice of -Wsign-compare" am: 1545889256 am: c1c27d597c am: 361384c81d am: 585ad4f655

Original change: https://android-review.googlesource.com/c/platform/system/tools/sysprop/+/1613110

Change-Id: I205aaa4e6fbc4886c09924832ddafe219925f027