title: /proc/cmdline does not updated with update-grub
body: <p>I am testing kdump functionality based on a ubuntu distribution(ubuntu-14.04.1-desktop-amd64), and found that with the following step, the /proc/cmdline does not get updated:</p>
  
  <p>1: modify /etc/default/grub[1]</p>
  
  <p>2: sudo update-grub</p>
  
  <p>3: reboot</p>
  
  <p>After a reboot, cat /proc/cmdline[3] does not have what I have changed in /etc/default/grub, while the boot cmdline in /boot/grub/grub.cfg[2] do show what I have changed.</p>
  
  <p>Any expert have some idea? Thanks a lot</p>
  
  <hr>
  
  <p>[1]manually modified in /etc/defaut/grub</p>
  
  <p>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash <em>foo=bar crashkernel=256M</em>"</p>
  
  <p>[2]automatically updated grub.cfg</p>
  
  <p>/boot/vmlinuz-3.13.0-32-generic root=UUID=9e93b3d1-2859-473c-9c1f-204c2bb4e4f5 ro  quiet splash <em>foo=bar crashkernel=256M</em> $vt_handoff</p>
  
  <p>[3]cat /proc/cmdline</p>
  
  <p>eric@eric-test-kdump:~$ cat /proc/cmdline 
  BOOT_IMAGE=/boot/vmlinuz-3.13.0-32-generic root=UUID=9e93b3d1-2859-473c-9c1f-204c2bb4e4f5 ro quiet splash vt.handoff=7</p>