Option force no password when launching images on providers

Images may return passwords from Nova. I have seen this happen with the official fedora openstack image as well as other times.
When SSH is used to connect, the password from nova is used, which results in authentication errors while you might want to use the ssh-agent for authentication.

To fix this I suggest the "forceNoPassword" option, to force the password to be empty even if we receive a password from the provider. This option is by default "false" and can be set in RunScriptOptions or TemplateOptions.

Github: https://github.com/jclouds/jclouds/pull/486