coreos-base/oem-gce: change some host bind mounts

This drops two mounts that are not needed anymore, since the ACI is
built with emerge and gets those data dependencies now.  It adds a
new mount for home directories to be created.

Two existing mounts remain: one for /etc, and one for /run/systemd
so the /dev/log link works.

sdk_container/src/third_party/coreos-overlay/coreos-base/coreos-oem-gce/files/manifest.in

@@ -13,21 +13,16 @@
     "group": "0",
 
     "mountPoints": [
-      {
-        "name": "baselayout",
-        "path": "/usr/share/baselayout",
-        "readOnly": true
-      },
-      {
-        "name": "cacertificates",
-        "path": "/usr/share/ca-certificates",
-        "readOnly": true
-      },
       {
         "name": "etc",
         "path": "/etc",
         "readOnly": false
       },
+      {
+        "name": "home",
+        "path": "/home",
+        "readOnly": false
+      },
       {
         "name": "runsystemd",
         "path": "/run/systemd",

sdk_container/src/third_party/coreos-overlay/coreos-base/oem-gce/files/units/oem-gce.service

@@ -17,9 +17,8 @@ ExecStart=/usr/bin/rkt run \
     --insecure-options=image \
     --net=host \
     --stage1-path=/usr/lib/rkt/stage1-images/stage1-fly.aci \
-    --volume=baselayout,kind=host,source=/usr/share/baselayout,readOnly=true \
-    --volume=cacertificates,kind=host,source=/usr/share/ca-certificates,readOnly=true \
     --volume=etc,kind=host,source=/etc,readOnly=false \
+    --volume=home,kind=host,source=/home,readOnly=false \
     --volume=runsystemd,kind=host,source=/run/systemd,readOnly=false \
     /usr/share/oem/coreos-oem-gce.aci