clone: Correct formatting of init message

clone: Correct formatting of init message

We used the wrong format method, which lead to this confusing output:

  $ ./jgit clone git://...
  Initialized empty Git repository in {0}
  remote: Counting objects: 201783
  ...
  remote: {0}

We need to use MessageFormat.format() as the message translations
use {0} syntax and not %s syntax for placeholders.

Change-Id: I8bf0fd3f7dbecf9edf47419c46aed0493d405f9e
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>