Merge master@5428150 into git_qt-dev-plus-aosp.

# Clean up old location of system_other.avbpubkey

$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/etc/security/avb/)

# Clean up bufferhub files

$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/bin/hw/android.frameworks.bufferhub@1.0-service)

$(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/etc/init/android.frameworks.bufferhub@1.0-service.rc)

$(call add-clean-step, rm -rf $(PRODUCT_OUT)/super.img)

# ************************************************

# NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST

# ************************************************