We got a report from a user in which ptp was set in the persistent config, likely from a previous version. This causes errors in the usb state and is not removed by an ota. To fix, remove ptp in the same place that mtp is removed from the persistent config. Bug: 62202885 Test: Add ptp to persistent config, verify removed. Change-Id: I5ebd93b9c8a49bcaca5a3362e49ed1e1acf50a9b