enable parallel user creation in ccng

Change-Id: Ifba19e1f8df40b6a4ae6a1102c10a1362597d60e
Signed-off-by: michael zhang <zhangcheng@rbcon.com>
Reviewed-on: http://reviews.cloudfoundry.org/13181
Tested-by: CI Master <cf-ci@rbcon.com>
Reviewed-by: Pin Xie <pxie@vmware.com>