Perform legacy global lock in addition to new per-account lock

We simply lock OfflineImap the same global way that we have always done
in addition to the previously implemented per-account lock. We can keep
both systems in parallel and then after a few stable releases, drop the
old-style global lock. by reverting this patch

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

offlineimap/accounts.py

@@ -172,6 +172,7 @@ class SyncableAccount(Account):
 
     def lock(self):
         """Lock the account, throwing an exception if it is locked already"""
+        # Take a new-style per-account lock
         self._lockfd = open(self._lockfilepath, 'w')
         try:
             fcntl.lockf(self._lockfd, fcntl.LOCK_EX|fcntl.LOCK_NB)