HI,
If you configure the VC for Provisioning through Airwave, Image upgradation should happened automatically.
Step 1 : Add the VC in Airwave
Step 2 : Configure DHCP option 43 and 60 properly
Step 3 : Upload all the Images (of all the platforms) to the Airwave
When there is Image mismatch found VC will send Image update string to the slave so that it can down load the suitable Image from the Airwave.
For you ref :