Change default size of storage pool to 15GB

Change-Id: I80a6801cc25003c3f7d5783853d014c509189376
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/installers/lxd-preseed.conf b/installers/lxd-preseed.conf
index 82ed8dc..21851d5 100644
--- a/installers/lxd-preseed.conf
+++ b/installers/lxd-preseed.conf
@@ -23,7 +23,7 @@
   type: ""
 storage_pools:
 - config:
-    size: 100GB
+    size: 15GB
   description: ""
   name: default
   driver: zfs