grub concole=hvc again in place

Hello
I have successfully migrated an hundred of xen vm (debian 4/56/7) to proxmox, using xenmigrate_new.py.
I have cleared /boot/grub/grub.cfg by any occurence of console=hvc and inittab as well.
Now that I have more than 1 hundred of vm running, I ma noting che after some time and after some events, in /boot/grub/grub.cfg
console=hvc
is still there. Maybe when I upgrade with apt-get upgrade and new kernel is installed...I dunno.
Sadly it is still there.
How can I get rid of it for ever and ever?
Thx