Revert my previous change which caused a regression and pass 'vnc' argument
instead of 'vnc:ip' to the API when vnc_password is provided.

Reference: http://www.elastichosts.com/cloud-support/api


git-svn-id: https://svn.apache.org/repos/asf/libcloud/trunk@1440132 13f79535-47bb-0310-9956-ffa450edef68