Fix minor bugs in snapshot removal, check it in tests

src/mock/messenger.cpp

@@ -15,7 +15,7 @@ osd_messenger_t::~osd_messenger_t()
 {
     while (clients.size() > 0)
     {
-        stop_client(clients.begin()->first, true);
+        stop_client(clients.begin()->first, true, true);
     }
 }