vmount: correctly set control_data output arg
vmount: correctly set control_data output arg

The control_data pointer wasn't correctly set for the cases where there
actually was a change/command.

PX4/Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,dagar/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,acfloria/Firmware,mcgill-robotics/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,mcgill-robotics/Firmware,acfloria/Firmware,Aerotenna/Firmware,krbeverx/Firmware,dagar/Firmware,PX4/Firmware,PX4/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,mcgill-robotics/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,krbeverx/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,dagar/Firmware,krbeverx/Firmware,Aerotenna/Firmware,PX4/Firmware,dagar/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,PX4/Firmware,acfloria/Firmware,krbeverx/Firmware,PX4/Firmware,krbeverx/Firmware,jlecoeur/Firmware,dagar/Firmware,jlecoeur/Firmware,jlecoeur/Firmware,acfloria/Firmware,dagar/Firmware,jlecoeur/Firmware,Aerotenna/Firmware,krbeverx/Firmware