MPC: initialize hover thrust with parameter even if using HTE
MPC: initialize hover thrust with parameter even if using HTE

The hover thrust estimator (HTE) starts to run after the first thrust
setpoint is published. Until then, the feedforward of the vertical
velocity controller was unitialized (= 0). This is now set to hover
thrust parameter until the estimate is available.

krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,PX4/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,PX4/Firmware,acfloria/Firmware,PX4/Firmware