Prevent stats logging compat change check unless reportChange explicitly called.

This is to reduce the volume of data upload.

Flag: EXEMPT doesn't impact device behavior
Bug: 157464257
Test: CtsAppCompatHostTestCases
Test: $ANDROID_BUILD_TOP/frameworks/base/ravenwood/scripts/run-ravenwood-tests.sh -s

Change-Id: Ifa5866c3d3b881e7ff15de768b29d77ac37c76db