Added reverse sync

Change-Id: Ied5dc10b4b92d900ba8a3f5f88ff64ba68c0804c
Signed-off-by: lloretgalleg <illoret@indra.es>
diff --git a/osm_common/fsbase.py b/osm_common/fsbase.py
index 24eb994..e15f7a5 100644
--- a/osm_common/fsbase.py
+++ b/osm_common/fsbase.py
@@ -85,3 +85,6 @@
 
     def sync(self, from_path=None):
         raise FsException("Method 'sync' not implemented")
+
+    def reverse_sync(self, from_path):
+        raise FsException("Method 'reverse_sync' not implemented")