assistedcontrol: Fix neutral throttle adjustments

1. Fixed neutral throttle adjustment and tested setting neutral to 0.4.  It auto calculted the required adjustment was 0.1 to get back to 0.5
2. Increased I term from 0.01 to 0.1 was required to make vertical hold effective avoiding large height deviations. Also 0.01 prevented auto-adjustment from calculating a material offset.