When adb is enabled, there's no need to also enable MTP mode. ADB mode enabled is sufficient to get connect messages from the kernel driver. This change modifies getDefaultFunctions() to return adb mode if adb is enabled, but mtp when it's not enabled. Also stop using "none" mode as the default. "none" should only be used when toggling the driver. Bug: 21429947 Change-Id: I767491417c6c69a120fcf4f3d6ec0c73311a1a60