Now grub2 is standard nearly everywhere and it makes a good job detecting what kernels are installed in /boot and if there is only one, boot from it.
My hosting provider system is pretty good: You have special customized kernel, the same one among all the linux distros, so you can run very old ones with a new secure kernel.
But I wonder if I wont use virtualization through VirtualBox, So I have to change VirtualBox modules each time I have a new kernel and it's not handy. openSUSE provide the module with every new kernel.
To get rid of the provider kernel I had to remove the /etc/grub.d/06-something-ovh config file and install the default kernel with YaST. Configure the boot system with YaST and reboot. The file is only used if it's executable, so "chmod a-x" is enough to make it unavailable (and easily recovered if necessary) .
It's still possible to use netboot to boot from external kernel if ever a problem arise (but without virtualization - anyway I wont use virtualization right now).