Linux MFS: fix handling of root UUID for Ubuntu
Linux MFS: fix handling of root UUID for Ubuntu

Make sure we replace all instances of the old root UUID with the new
one when modifying the bootloader config file.  Ubuntu uses the grub
'search' command to set the root variable based on the UUID.  If it's
wrong, grub fails to boot.

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome