JCLOUDS-619

Hello,

this is the fix for the issue described here[1].

Please review and let me know if you need something else.

Thanks and kind regards
Markus

[1] https://issues.apache.org/jira/browse/JCLOUDS-619
It should be pretty straightforward. Just annotate the `MultipartNamingStrategy` as `@Singleton`, as it does not have state and it seems like a good singleton candidate, and add it as a parameter to this class constructor. That's it! :)
You can also consider extracting an interface, and annotate it with the `@ImplementedBy` annotation pointing to the default implementation, but given that currently there is only one, I don't think this is necessary.