Increase vagrant vm's memory size

Vagrantfile

@@ -21,7 +21,7 @@ SUPPORTED_OS = {
 $num_instances = 3
 $instance_name_prefix = "k8s"
 $vm_gui = false
-$vm_memory = 1536
+$vm_memory = 2048
 $vm_cpus = 1
 $shared_folders = {}
 $forwarded_ports = {}