SGTools: Fix dummy proxy leak.

When we remove a proxy, be sure to decrement the reference count even
if it's not in m_storeMap.  A dummy proxy won't have been entered
there, but it will still have gotten a reference count.

Control/SGTools/src/DataStore.cxx

 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
 
 #include "SGTools/DataStore.h"
@@ -208,12 +208,17 @@ DataStore::removeProxy(DataProxy* proxy, bool forceRemove, bool hard)
     int index = it->second.first;
     sc = StatusCode::SUCCESS;
 
+    // Remove primary entry.
     m_keyMap.erase (it);
     if (storeIter != m_storeMap.end()) {
       if (1 == storeIter->second.erase(name)) {
         proxy->release();
       }
     }
+    else {
+      // A dummy proxy.
+      proxy->release();
+    }
 
     // Remove all symlinks too.
     for (CLID symclid : clids) 

Control/SGTools/test/DataStore_test.cxx

 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
-
-// $Id$
 /**
  * @file DataStore_test.cxx
  * @author scott snyder <snyder@bnl.gov>
@@ -512,6 +510,24 @@ void test_dummy ATLAS_NOT_THREAD_SAFE ()
   assert (dp2->clID() == 456);
   assert (dp2->name() == "dp2");
   assert (dp2->refCount() == 1);
+
+  SG::StringPool::sgkey_t sgkey3 = pool.stringToKey ("dp3", 456);
+  SG::DataProxy* dp3 = make_proxy (0, "", sgkey3);
+  assert (store.addToStore (0, dp3).isSuccess());
+  assert (dp3->refCount() == 1);
+  assert (store.proxy_exact (sgkey3) == dp3);
+
+  dp1->addRef();
+  dp2->addRef();
+  dp3->addRef();
+  assert (dp1->refCount() == 2);
+  assert (dp2->refCount() == 2);
+  assert (dp3->refCount() == 2);
+
+  store.clearStore (true, false, nullptr);
+  assert (dp1->refCount() == 1);
+  assert (dp2->refCount() == 1);
+  assert (dp3->refCount() == 1);
 }