TT#11444 Depend on grub-pc *or* grub-efi-amd64 to support EFI systems

Otherwise when deploying to a system with EFI support
grub-efi-amd64 gets removed and leaves an unbootable system
behind.

Change-Id: Idd359a2916369e75598ec18b01ce40582ac061a4

debian/control

@@ -275,7 +275,7 @@ Depends:
  exim4,
  glusterfs-client,
  glusterfs-server,
- grub-pc,
+ grub-pc | grub-efi-amd64,
  haproxy,
  haveged,
  heartbeat-2 (>= 2.1.3-7~sipwise2),
@@ -378,7 +378,7 @@ Depends:
  bzip2,
  dbus,
  ethtool,
- grub-pc,
+ grub-pc | grub-efi-amd64,
  haveged,
  iptables-persistent,
  kannel,
@@ -465,7 +465,7 @@ Depends:
  exim4,
  glusterfs-client,
  glusterfs-server,
- grub-pc,
+ grub-pc | grub-efi-amd64,
  haproxy,
  haveged,
  heartbeat-2 (>= 2.1.3-7~sipwise2),