Add closers for persistent store backend

shep/store/file.py

@@ -154,3 +154,7 @@ class SimpleFileStoreFactory:
             if re.match(re_processedname, v):
                 r.append(v)
         return r
+
+
+    def close(self):
+        pass

shep/store/redis.py

@@ -96,3 +96,7 @@ class RedisStoreFactory:
     def add(self, k):
         k = str(k)
         return RedisStore(k, self.redis, binary=self.__binary)
+
+
+    def close(self):
+        self.redis.close()

shep/store/rocksdb.py

@@ -119,3 +119,8 @@ class RocksDbStoreFactory:
     def add(self, k):
         k = str(k)
         return RocksDbStore(k, self.db, binary=self.__binary)
+
+
+    def close(self):
+        self.db.close()
+