mbnames should write out local and not nametransformed box names

Rather than to write out the nametrans'lated folder names for mbnames,
we now write out the local untransformed box names. This is generally
what we want. This became relevant since we support nametrans rules on
the local side since only a short time. Reported by Paul Collignan.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/accounts.py

@@ -372,7 +372,7 @@ def syncfolder(account, remotefolder, quick):
                          % localfolder)
             return
         # Write the mailboxes
-        mbnames.add(account.name, localfolder.getvisiblename())
+        mbnames.add(account.name, localfolder.getname())
 
         # Load status folder.
         statusfolder = statusrepos.getfolder(remotefolder.getvisiblename().\