fix(builder): don't reload cedarish if its already loaded

Ref #1643

Also add log messages

Author: Sam Dodrill

builder/bin/boot

@@ -55,7 +55,12 @@ done
 
 # HACK: load progrium/cedarish tarball for faster boot times
 # see https://github.com/deis/deis/issues/1027
-docker load -i /progrium_cedarish.tar
+if ! docker history progrium/cedarish >/dev/null 2>/dev/null ; then
+	echo "Loading cedarish..."
+	docker load -i /progrium_cedarish.tar
+else
+	echo "Cedarish already loaded"
+fi
 
 # pull required images