updated to use centos 7 drawfork image

gce-properties.yml

diff --git a/gce-properties.yml b/gce-properties.yml
index edc6681..23154e7 100644
--- a/gce-properties.yml
+++ b/gce-properties.yml
@@ -5,7 +5,8 @@
 #machine_type: 'n1-standard-4'
 machine_type: 'n1-standard-2'
 #image: 'centos-7-v20180104'
-image: 'centos-7'
+image: 'centos-7-drawfork'
+#image: 'centos-7'
 #image: 'centos-7-v20170918'
 #image: 'centos-7-v20160511'
 #image: 'centos-6-v20170918'