client:

- mkfs.xtreemfs does not set owner user and group if not explicitly specified at command line (fixes issue 204).
- rmfs.xtreemfs allows to specify the user mapping (needed to successfully delete a volume unless user certificates are used).
- lsfs.xtreemfs now sends bogus user credentials to the MRC.

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2645 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534