Fill out bootloader pkg-map

Our bootloader install fails on non-gentoo builds due to missing pkg-map
for grub-pc. This map should really live in the bootloader element, so
move it there and fill it out.

Change-Id: Ib11b9df84b593ab25232729a570c812f1b4b8774

elements/base/pkg-map

@@ -5,11 +5,6 @@
     },
     "suse": {
       "dkms_package": ""
-    },
-    "gentoo": {
-      "dkms_package": "",
-      "grub-pc": "grub",
-      "extlinux": "syslinux"
     }
   },
   "default": {

elements/bootloader/finalise.d/50-bootloader

@@ -19,7 +19,7 @@ else
 fi
 
 function install_extlinux {
-    install-packages -m base extlinux
+    install-packages -m bootloader extlinux
 
     echo "Installing Extlinux..."
 
@@ -59,9 +59,9 @@ function install_grub2 {
     if [ -f "/tmp/grub/install" ] ; then
         source /tmp/grub/install
     elif [[ "$ARCH" =~ "ppc" ]]; then
-        install-packages -m base grub-ieee1275
+        install-packages -m bootloader grub-ieee1275
     else
-        install-packages -m base grub-pc
+        install-packages -m bootloader grub-pc
     fi
 
     # XXX: grub-probe on the nbd0/loop0 device returns nothing - workaround, manually

elements/bootloader/pkg-map

@@ -0,0 +1,17 @@
+{
+  "family": {
+    "gentoo": {
+      "dkms_package": "",
+      "extlinux": "syslinux",
+      "grub-pc": "grub"
+    },
+    "suse": {
+      "dkms_package": ""
+    }
+  },
+  "default": {
+    "dkms_package": "dkms",
+    "extlinux": "extlinux",
+    "grub-pc": "grub-pc"
+  }
+}