disk_util: support exposing a hybrid partition without syslinux
disk_util: support exposing a hybrid partition without syslinux

We don't need to do anything like manually install the MBR boot code
for grub but we do need to continue to expose the ESP partition as a
hybrid partition to support pvgrub.

smilart/scripts,gtank/scripts,BugRoger/scripts,andrejro/coreos--scripts,trnubo/scripts,endocode/scripts,zhang0137/scripts,glevand/coreos--scripts,endocode/scripts,zhang0137/scripts,endocode/scripts,fivethreeo/scripts,smilart/scripts,BugRoger/scripts,BugRoger/scripts,mischief/scripts,marineam/coreos-scripts,gtank/scripts,smilart/scripts,trnubo/scripts,fivethreeo/scripts,glevand/coreos--scripts,marineam/coreos-scripts,mjg59/scripts,coreos/scripts,nicescale/scripts,vmware/coreos-scripts,trnubo/scripts,coreos/scripts,andrejro/coreos--scripts,nicescale/scripts,gtank/scripts,mischief/scripts,vmware/coreos-scripts,andrejro/coreos--scripts,nicescale/scripts,sigma/coreos-scripts,marineam/coreos-scripts,sigma/coreos-scripts,zhang0137/scripts,fivethreeo/scripts,mischief/scripts,mjg59/scripts,vmware/coreos-scripts,sigma/coreos-scripts,mjg59/scripts