Initialize mLayoutOverlayApplied

This variable is left uninitialized. On some platforms, this causes the
libinput_tests to fail when sanitizers are enabled.

Bug: 251249010
Test: m libinput_tests && adb sync data && adb shell -t /data/nativetest64/libinput_tests/libinput_tests --gtest_filter="*keyCharacterMapParcelingTest*"
Change-Id: I05063efdde9a826f7001dca828b84bbec5beb0df