MagFieldServices: Clean up conditions dependency.

Don't declare a dependency on the DCS conditions folder if we're
not going to use it.

MagneticField/MagFieldServices/src/AtlasFieldCacheCondAlg.cxx

@@ -40,7 +40,7 @@ MagField::AtlasFieldCacheCondAlg::initialize() {
     ATH_CHECK( m_condSvc.retrieve() );
 
     // Read Handle for the current
-    ATH_CHECK( m_currInputKey.initialize() );
+    ATH_CHECK( m_currInputKey.initialize (m_useDCS) );
 
     // Read handle for the field map cond object
     ATH_CHECK( m_mapCondObjInputKey.initialize() );